Do your best with accomplishing the following:
#1 Trustability and Likability – My market is quite skeptical about products such as mine due to a lot of keyloggers and viruses being found in addons. There is also a bit of a taboo attached to selling addons. It’s looked down upon. So, trustability and likability is a big factor in the design. They should know we're not bad guys. I think 90% of this can be achieved by just having a professional clean looking design. But besides for that, I think using images and graphics that give off a ‘friendly’ feeling can also help.
#2 Cool – My gamer audience is definitely not afraid of a little extra sexiness. When they see the design I want them to say, “Oo, that’s pretty cool”. And by cool, I don’t mean explosions and fireworks. Personally, I find things to be cool when something is creative, unique, and slightly different from everything else.
Unfortunately, Blizzard will not allow us to use any images of their characters due to copyright reasons. However, they don’t seem to mind if people use environmental images of the game.
Creating beautiful custom images/graphics is going to be a big plus rather than using stock stuff.