I downloaded this app thinking it would turn photographic textures into tessellated textures.

That's not what it does.

What it does do is create complex repeatable patterns based on mathematics which you control graphically (so you don't need to know any maths) but which you can also edit algorithmically (either because you understand the maths, or it's just fun to experiment.

It's simple to use, produces gorgeous results, and has a tiny footprint. And it's free.

It doesn't really get much better than this.