I finally made myself a new shirt using the pattern I made a couple of weeks ago, and I'm really happy with the results.
I decided to add a pattern to the fabric by laying some lace over it and then spray painting the whole thing - the spray paint passes through the holes in the lace, and you're left with a negative version of the lace pattern. The picture above is one of my test swatches.
Spray-painted fabric is surprisingly durable in the wash - I just throw mine in the washer and dryer with the rest of my clothes. It will probably fade over time but, really, I can always make a new one!
The only downside I have found is that sometimes you get a lingering scent of spray-paint coming off the shirt, but I'm sure that will fade after a handful of washes. I am so happy with the way this project turned out!