For improve the appearance to become moe appealing I'll use flat design like windows metro (more or less)
And for avatars, I just need to modify the database so thatit allow us to change vendor avatars. And because vendor and post are correlated, so when we join those both table, it should be return posts with specified vendors.
I suggest you to use custom CMS, not using wordpress or kind like that, because we can easily define what we needed and install what we are looking for.