Comment 4 for bug 296414

Sorry, but I have to make two corrections to that.

The actual IMAGE, which is currently required and is used as by the thumbnailer, can be any size you wish. Somewhere below 1600x1200 would be best for bandwidth. The width should also be greater than or equal to 125px so that it is large enough for the largest thumbnail. So, 500px wide is a good example, but not required. You can just keep it your native screen resolution.
Now that I think of it... that range would be helpful to put in the 'help' right below the field.

I would like to get it to accept other formats like pdf and odf, but I cannot really figure out how to do that. I have no doubt that it is possible, I just don't know how to do it. It will require quite a bit more research and time for me to figure out.