Basically, you are designing an Official Benheck T-shirt/Merchandise design, to sport while sitting in your basement in the dark on your computer. I know you don't get out much. Yes, I'm talking to you. (:shock: How duz he noe!?11 )
Of course, there are limitations. T-shirts usually can't print in full colour for cheap, so try to keep it less than 5 colours.
Now, black shirts or dark colours are the most common for us nerds to wear, so if you draw with a dark background, go for it.
Best is a monotone design that can be inverted for light shirts.
Go wild! You have a week or two, I guess.
)