One thing not to forget when cooking lamb, is to season well. The meat is somewhat bland. More than usual pepper and salt and herbs of your choice. I do like quite a lot of garlic, rosemary or fresh tarragon with lamb.
Some nice additions; Lamb and beans are so delicious! Best sauce with rack of lamb is still... nothing or a sauce Choron (Béarnaise + a little tomato paste). Roasted tomatoes and potatoes. Etc.
Here's a few dishes I made in the past. A few pictures look a bit dated.
Moussaka made with lamb minced meat, aubergine, potato, Mornay sauce
Rack of lamb, beans, rösti, mustard sauce
Lamb chops, roasted potato and tomato, sauce Choron
Slice of gigot (lamb leg) with cauliflower and Hollandaise
Rack of lamb, flageolet beans, flan of mushrooms, pommes Parisiennes, endives
Gigot with stuffed aubergine and roasted tomato