I'm kind of a sucker for hanging my art in a collage-like fashion. This trend has been great for me because my house has very little wall space (lots of doors and pass-throughs) and I have a lot of meaningful art I want to display.
There are a lot of helpful tricks to the trade out there. One good one is laying everything out on the floor so you get an idea of where you want to place your pictures.
As you can see, I switched it around a bit once I started putting them up on the wall.
More frequently, I just start slightly off center with a focal point, and then build around it. I like adding different textures and types of media to keep things interesting. A lot of my art work is done by family members, or items I've repurposed. Mirrors are also great add-ins and bring light into dark spaces.
Really there's no rhyme or reason, but I try to keep everything close together so it looks like it's part of a whole. Items hung too far apart lose their collage effect. Make sense?
The best part is, I can switch pictures in and out of the configuration for a quick change.