Ok - I have permission pending on the Z4 roadster image - but like a few have pointed out, the site uses the E89 as it's logo - so maybe that's the way forward?
Anyways - to respond to a few questions or points (in no particular order

):
● I wouldn't be selling these with any mark-up. The price I charge would be the price I buy them at
● In regards to a less graphic design - I know what you mean, but the problem we face is that the forum doesn't have a logo that lends itself to being in a less-graphic environment unlike PistonHeads. They're at a great advantage, as the PH logo is "unique" to them, and it's also a monotone image - making it a piss-easy job to create a subtle design that incorporates their branding.
Here we're kinda stuck, as our logo is a Z4 - and in it's very nature, it carry's more brand identification to BMW than to our forum.
To counter that, I believe we need the forum address to be predominant in the design.
But with all that said, I don't claim to know what I'm doing in regards to branding.
I'll see if I can pull a "less graphicy" one out of the bag anyways
● I'll have a think and see if I can work out a couple of different designs along the same theme (so we're keeping a "brand"), which may break up the concerns with everyone wearing the same if it's considered a problem big enough to stop people buying?
● Adding an image to the back doesn't increase cost if you look around. Initially I was going to just have a front badge, but as it didn't cost anything extra - I added a back one
● I did try the name on the front, but it didn't really work (it looked very much like a "hello my name is..." :thumbsdown: ).
I had a crafty scout at other forum and group tees, and the popular idea is the name on the back - so I think I'll be sticking with that
● I could extend the name on the back to have two lines of text - one for the forum name and one for the real name?
● Size-wise, the handful of places I've short-listed to get these printed have sizes ranging from ladies size 6 to men's XXXL?
● You can call me "Esskay" as much as you like - I've had the "name" for 17 years, so I'm use to it

(And it's better than being called Craig or Matt all weekend

)