You don't wanna read my guess: you never tried the demo of the tool I mentioned.

I have a library of self-made photo textures for "Running Food"/"World of Dice" of 100 made with photoshop (I didn't know of STG from the beginning) and at least 200 self-made textures made seamless with the Generator. Using the Seamless Texture Generator doesn't prevent you from thinking about the best frame and the best perspective and from testing whether the texture looks appropriate, but it needs only 5 steps where you otherwise need at least 30.