Yes, you can rename them on SkyDrive or anywhere else. But not on the device, apparently. I regard this as a flaw.
Example: In January I spent two weeks in Taiwan and took almost 300 pictures with my BlackBerry (I didn't have the Radar yet). Many of these photos were in places with names that I couldn't remember for long. I renamed them as I went along, while the memory was fresh. I didn't upload them anywhere until I returned to the US.
I couldn't have done this with the Radar.