To see what I mean, check out the below graphic. This is just the logo for my WoW guild - but keep in mind, I did NOT put the background color into it. The drop shadow is dynamic transparency.
![Image](http://www.unitedorderofvirtue.org/phpBB2/templates/Chronicles/images/logo_uov.png)
The only downside I can really see is that doing a right-click>save as.. with Internet Explorer will try to save the overlayed graphic, not the main one. Easy to rectify, as you can do a quote on the post in question to get the original image location.
Or you could... you know, switch to FireFox.
![Happy :)](./images/smilies/happy.gif)