In a new group I joined we are having a challenge: paint using the geometric shapes of circles, squares and triangles only. It can be totally abstract or more realistic (using the moon as a circle, a table as a square, etc.). This began as a poured fluid acrylic and gesso painting that wasn't going anywhere. So I worked it a bit more and came up with this. Everyone agreed you can see the circles and triangles but the squares are harder to see. (You can see them in the painting if you're standing in front of it, though.) This is Streaming Red Cliffs - so those are waterfalls, of course! ha ha
I really don't know what I'm doing with acrylics - and it shows.
How about this abstract I did with glued paper and different elements. It's very 3D because the paper I painted on is 3D - lots of texture and elements pushing out from the paper underneath.