I always tried to keep my post styles small. One picture at most. I like it when they're smaller than the length of my post (in text). Back in the day, when I was getting really into it, I would have 2 different post styles. One for "long posts" and one for "short posts".
Nowadays, if I have a short post, I just don't use any post style at all. Laziness has to do with it. Readability and just the way it looks has to do with it. Back when the GCD was big on post styles, it did get quite obnoxious and I can see how the negativity spread.
Overall though, unless your post style is text (which are the type of post style I hate the most, tbh), it's only beneficial to have one if you have a permanent avatar or character. With someone who changes avatars frequently, the post style doesn't match the avatar. And then it looks weird, to me.