Well, in that case, try our plug-in for QuickLook: MBS-Xojo-QuickLook-Plugin.dmg
After installation of our plug-in to /Library/QuickLook and you restarting the Finder or logged in the next time, your icons look like this:
Enjoy! This plug-in is freeware, so tell your friends. Version 1.4 adds support for newer Xojo versions.