I am no photographer, but I believe nicoledphoto has some great ideas. May I also suggest the following:

1. clouds
2. antiques
3. down to earth
4. urban life
5. rural life
6. suburban life
7. textiles
8. rainbows
9. technology
10. next generation
11. old and new
12. to have and to hold (not including weddings)
13. determination
14. hope
15. charity
16. the “good ole days”
17. Aerial photography