Rasmus Rasmussen, an experienced iStock inspector (among other things), has a great post on his blog called “10 Subjects to Water Down Any Portfolio.” His biggest pet peeve is listed below:

1. Bugs on Flowers

Congratulations on your macro lens. At least I hope you used a macro lens, so you could get somewhat close. Bugs on flowers is my personal pet peeve subject. Sure, flowers are pretty and bugs are interesting creatures, but as a photo it just doesn’t do it for me. Most of the time, it comes out looking like you were just practicing and like the gazillion existing images just like it.

For the remaining nine, read the full post at his blog.