The most popular community sites are the least attractive. There's too much copy, no clear call to action, and few images.
The only common trait of almost all super-successful community platforms is they put function far ahead of form. They put the latest activity far above any images. They refuse to let anything, anything!, get in the way of members doing what they came here to do.
They don't worry if the sites are visually appealing. They worry if as much space as possible is given to showing what's new and popular in the community at any one time. They worry if members can easily see where to register and reply to discussions.
It's not easy to do this.
Your boss, your colleagues, your spouse, your friends, and acquaintances will complain the site doesn't look enough like the content sites they love.
That's a good thing. You're not developing a content site. A community site is going to look an awful lot like a community site – so crammed full of activity there's no space to waste on images.
If you feel yourself being tempted to add big, attractive, images, visit Reddit again.