No photo is displayed for incoming calls - am I missing something?

I have the iPhone 4 for Verizon. For some odd reason, despite the fact that all of my contacts have photos assigned to them, no picture is displayed when someone calls. I can't figure out how to adjust the settings so I can see a picture rather than just their name. I haven't seen anything in the settings or userguides or forums. This has been driving me nuts for months and I feel like an idiot for not being able to figure it out.

Does anyone have any ideas for adjusting the settings or something so I can "see" my callers? 😕

Thanks so much,

Ali