I know a while back MarcelG had put together a mini-mod to limit the size of Signatures... you might want to look at that and see if you could further extend it for images in posts.
There is a good one floating around that uses javascript to resize to a pre-specified width and also creates a click to enlarge link. See how it works here...
I'm having problems getting it to resize the images on the page. The popup works and using the new .js from Marcel it is in a browser window now but the images posted are still not downsizing to the size I've set in the .js :( I'm testing offline but it isn't working :(
I've followed the instructions but I think I've missed the obvious?!?!?
Symon, please revert back to the original inc_func_common.asp, and re-apply the clipped urls mod before continuing this mod. You're now using a wrong version of inc_func_common.asp, which is not a good basis of the implementation of any other mod.