I do like art, though, and so do others. So, when designing the magazine, I decided it should have art, and it does, in a variety of styles. Some day, I may decide on a house style; until then, eclectic is my watchword.
Because I have no graphic talent myself, I have a very hands-off approach to cover creation. I usually pick a story I think would make a good cover, and then choose an artist whose style I think is a good fit. (I sometimes let the artist pick from among several stories, but I usually have one in mind as most appropriate.) Once the story's chosen, I send the artist one or several clips from the story, intended to a) set the desired scene, and b) provide enough information that the artist knows what there is to know.
I ask the artist for one or more concepts, give some feedback (sometimes administrative - "I need space for author names", sometimes opinion - "I like this one better"), and let them loose. Then there's a draft of the complete image, a few minor tweaks, and the thing is done.
Usually, the result doesn't look at all like what I originally imagined. That doesn't really matter, though. The artist is drawing on the same source material I am, and their interpretation is just as good as mine. Better, since they know how to draw.
There are drawbacks to this approach, of course. Sometimes, the resulting cover isn't really to my taste. Invariably, that's a cover that draws raves from others, so once I've selected an artist whose style I like, I broadly trust their judgment. Of course, the public is unpredictable. Once (and only once), an artist failed to produce anything. In that case, I whipped something together myself with GIMP and some photographs - and that also got good reviews. It worked, but I know my limits, and I use professionals whenever possible.