We're looking for an interesting and eye catching design incorporating the logos of open source software groups (i.e. Ubuntu, Debian, KDE, Tux, et al). All logos must have some sort of open source license like GPL, CC or BSD. There are some issues with licensing of the FireFox and RHEL logos, so avoid them.
We'd like to avoid having a Linux distribution specific design. One of our early designs is attached so you can get a feel for the kind of thing we want.
We plan to use white T-Shirts unless we find an intriguing design that uses another color. We're looking for something simple and bold with color and not too much text. Beware that we have some typography nerds, so no Comic Sans or proprietary fonts. The Ubuntu Font Family is a good choice http://font.ubuntu.com/
Other than that we need to leave some space on the back for the logo of our corporate sponsor.
Once again, we can't work with logos or fonts that aren't freely licensed.