If you have photoshop (you could possibly use other programs I dunno) then its very easy to make your own.
Unless you mean physically produce which for something like a nhex army is quite simple.
I am using gimp for the design and it's a simple and fun process, but I am not very handy and I don't trust myself to actually make good looking tiles. I've read a couple of technical instruction articles, it seems complicated, and judging by the pictures, when done RIGHT, the product looks great. I have a feeling if I tried, it would be a total disaster.
Just in case you're curious, or you've done this yourselves, I am indulging my gaming fetishes and producing a Tyranid army, a Duke Nukem army and a Doom army. I wrote 5 original armies but I have no artwork to apply to them.