I had fun thinking about it. (I'm not really a caterer myself, but I do work as a cook and server for a pretty big catering company. Does this mean it's okay for me to post here? I was a little worried about that...)
A few more ideas:
-Maybe a croque-monsieur/croque madame panini? There are different definitions of this, but I'm thinking of sandwiches on a sturdy bread, with ham and gruyere, dipped briefly in an egg-and-milk mixture, maybe sprinkled with a little parmigiano-reggiano, then finished on electric griddle or panini press. yum.
-Make your own pitas: Offer falafel, hummus, tahini, and assorted fresh vegetables. This is tasty for everyone, and vegetarians/vegans will especially appreciate it.
-Make your own gyros: Offer gyro-style meat and veggies, with tzatziki sauce. (Of course, you could also have servers do the assembly if that works better.)
-I don't know if this would work...but maybe you could do some kind of southern-style po'boy...like, maybe a fried catfish sandwich or wrap, served with hush puppies....Fish is so hard to hold successfully, though. I'm trying to think of something to honor the flavors of the southeast U.S, something in kind of a soul food or cajun tradition....I don't know. Anyone else have any ideas? Fried mac-and-cheese bites?
-I really do like the idea of the siu bao (I'm pretty sure that's what they're called: the steamed chinese buns, usually filled with barbecued pork). Have you ever had these? They're hearty, super-delicious, easy to carry around, and yet kind of unusual. You wouldn't even have to make them yourself if you didn't want to; I'm sure you could buy them in bulk and just heat them up on site in a chafer with a steamer insert. They're available with a variety of fillings, including vegetarian. (When I was in Japan, you could get vegetarian siu bao from a hot case at 7-11. soooo good!!)
Well, the OP mentioned a chinese chicken salad; I'm guessing it's served in cardboard takeout containers so that people can walk around with it more easily. So yes, I'm thinking you could get creative with the salads, but serve them in the same way...Maybe a Thai Beef salad, or a simple butter lettuce salad with bacon-wrapped cipollini (another Michel Richard idea)...there's a million different salads you could do.
Also, a lettuce wrap or lettuce cup thing might work...though these might be kind of labor-intensive. But the company I work for does lettuce cups buffet-style, with little cocktail plates, and these seem to work pretty well as walking-around cocktail-party food.
You could also do a Vietnamese-style spring roll in rice paper wrapping, and fill it with a delicious salad. Traditionally, they include shrimp, of course, and you could do that, too. Michel Richard has a recipe called "Romaine on Romaine" that might inspire you. Also, in Tyler Florence's Real Kitchen, there's a recipe for Vietnamese Shrimp rolls that are filled with a mixture of beets, carrots, bean sprouts, red chile, cilantro, peanuts, shrimp, and mint. If you left out the shrimp, these would still be very pretty, and they would also be vegan. (Whatever you may think of Tyler Florence, I do find that his recipes are consistently easy-to-follow, successful, and delicious.)
I'm interested to know more about the film crews you are working with. Are you just working with the tech crews--the gaffers and grips and whatnot? Or are you also serving the directors, PAs, and actors? Are these small productions or big ones?
I'm asking because the demographic might influence your menu. You say you're in California, so I'm guessing that it's a fairly ethnically diverse bunch. As such, they'd probably appreciate a range of international flavors & cuisines.
But...from the menu items you listed, it sounds like you are going for hearty and approachable, as opposed to sophisticated or unusual. Is there a reason for that?
Another thing I notice is how heavy it is on the bread--which makes sense, because you're looking for things that are easy to carry around.
But one thing I think a catering company can do to stand out is to consider possible dietary restrictions when planning this kind of buffet-style menu. Not just vegetarian options, but other special diets as well. So many people are modifying their diets for different reasons these days: vegan, wheat-free, gluten-free, dairy-free, low-carb, low fat, low sugar/diabetic...etc. (Even I, food geek that I am, have become part of this annoying trend: Though I will eat anything if I'm curious and/or hungry enough, I do try to avoid processed foods and wheat in my every day diet. So I am always very appreciative of wheat-free options.)
Maybe you are dealing with a group of people who don't appear concerned about dietary restrictions? That's why I asked who you're feeding: I'm guessing that your typical actor might be more likely to follow a restricted diet than your average key grip, but you never know! Especially if you're in SoCal!
So, I'm thinking you might consider:
For Wheat-Free, Gluten-Free, and Low Carb folks:
-Rice paper rolls
-Lettuce cups with a ground meat or chopped chicken filling (a lot of room for variations here).
Just make sure you use wheat-free tamari instead of regular soy sauce in these recipes. (These could also work for the dairy-free and vegan folks, if you modify the recipes accordingly.)
For the Vegetarian/Vegan Folks
-Falafel, hummus & tahini, served with pitas
-vegetarian/vegan chili (this can actually be pretty tasty).
For diabetics and dieters:
-Maybe a special low-sugar dessert (I don't believe in artificial sweeteners, but I've tasted some pretty delicious chocolate tortes and cheese cakes that were sweetened with a mixture of agave syrup and splenda).
Flourless chocolate brownies, assorted chocolate truffles, or a triple chocolate terrine made with layers of white, dark and milk chocolate ganache would work for the wheat-free folks. So would cakes made with almond meal instead of flour (I have a Nigella Lawson recipe for a white-chocolate almond cake that would fit the bill, but I haven't tried it yet.)
Okay. This is a fantastic way to procrastinate, but I better go get some work done!