I like the mouse pad and sticker ideas a lot - thanks for suggesting!
A range of sticker sizes like a car bumper sticker, then "Intel inside" size, and something in between would be cool.
I'm looking for something like this for quite a while now. I guess it's no problem to print some real decals (not only stickers) for tuning the HTPC-case (or even etch some 3D-Logo), but therefore you need a vectorized logo. Beside that the current MP-logo unfortunately is very thin (at least the "MediaPortal"-font), so I guess there could be some problems here...
There is an Shop about emule merchandising, also based on spreadshirt.net, where you can buy Cups, T-Shirts, underwear, and for sure a little emule doll.
I bought some t-shirts from the We're Alive podcast some time back and really love the feel of their fabric, it's so much smoother then most of the t-shirts I've bought in shops. Think the brand of the t-shirt is American Apparrel.