Pretty neat stuff. You may want to have people keep it below 5000 Bytes though, or even smaller. At long 50 post threads, that will slow down loading for those slower modems quite abit. Even at 5000 Bytes each, it would add 250Kb to a long thread, and would be equivalent to adding approx. 5-7 full photos that are normally posted on the Forums to the thread.

If you don't restrict it, some could have images as large as 50Kb or more, if they first don't pre-shrink them to proper size at their own source before linking to them. Alot of people may not realize that even though the images look small here, if they are linking to a larger image from their own source, it is equivalent to loading their full size image here too!