T-Shirts
I personally have already too many t-shirts, so I propose to have a special ceramic beer-mats with our own design.
To get an idea of what these ceramic beer-mats look like, have a look here: https://www.pivni-podtacky.cz/galerie/ and here: https://www.facebook.com/pivnipodtacky/photos/
They are hand made, except for the template that is carved by some computer controlled machine. Diameter is approx 11 cm, thickness 3/4 cm. Expected price 8-10 EUR. Possible colors vary depending on what colored glass is currently available, and it is never the same when it comes out of the furnace. Try to choose from the above picture, colors of rainbow, RGBW, CMYK, or any simple color names like brown, orange, grey, etc... Please avoid smells and tastes like mint and salmon ;-). Keep in mind that I have to translate them to the maker, and be prepared that it finally may be not exactly what you expected. Black is not recommended, as it tends to spill over the unglazed part. See bottom row 3rd from left on the above picture. Therefore also fully colored tux is not possible, unless we would use some other color instead of black. Small colored parts are also problematic. Colored glaze is applied in the form of small (1-2mm) pieces of glass on top of the beer pad and then "baked" together with the ceramics. That also means that thin glazed details are more problematic than thin unglazed details. Also it was recommended to use all-caps sans-serif font, for better readability of smaller letters. I prefer Tux to be as big as possible with text filling the empty spaces for two reasons - bigger details, and possibility to make variant without text (and then sell it to general Linux geeks or kids who like penguins).
Design A is based on https://en.wikipedia.org/wiki/Tux_(mascot)#/media/File:Tux_Classic_flat_look_v1.1.svg and design B is based on https://en.wikipedia.org/wiki/Tux_(mascot)#/media/File:Tux_Mono.svg (note the smiling beak). I think both licenses permit modifications and commercial use. The pale brownish/yellowish color is the unglazed ceramics, green is glazed and can be chosen as said above. Please state your preferences in the second sheet of accommodation spreadsheet.
A.
B.