I've recently created two different gallery walls - no money spent- by simply gathering various existing frames from the home and filling them with home-made art, personal photography, prints from old calendars, and vintage posters.
The first was at my parent's country home on the East Coast. The grouping is in all black frames to create unity.
This small gallery in a different corner of the same room groups wood frames. The pictures are from old calendars, and the leaves are from good ol' Mother Nature.
The next was in my powder room which has a blank white wall and a wallpapered wall behind the toilet. I wrapped the gallery around the two walls and mixed up the frames to add some interest to a small space like this.
Hope you are inspired to refresh a wall without purchasing anything new!