The stretched icon above is an example of what happens in this forum using the Opera browser version 9.5 beta , and I think the earlier non-beta version 9 and above.
This happens at seemingly times, and if I press reload, it will be ok when it is reloaded.
I posted about this problem in the Opera forum at http://my.opera.com/community/forums/topic.dml?id=214309
There haven't been any very useful responses to that post.
It seems fairly clear to me that it's not the images that are the problem, it's either an outright defect in Opera, or something about the code for these forums is slightly eccentric and instead of sucking it up and displaying it right like internet explorer or firefox would, opera insists on being literal and giving you a defective page.
It's possible that the presence of user javascript might have some bearing on this problem.
I've been using the script that Strife wrote to display the vBcode correctly. Today I hid that script and replaced it with LinkifierPlus from userscripts.org and the gif texture stretching persists.