It all depends for the embroidered patches.
Most of the one that are cheaper (and competitive, if you equate cheap with competitive, which most do as patches were the first aspect in the embroidery process to reach commodity status), if they do allow for custom, you have to use stock shapes (circles and rockers mainly, although you do get some shield type shapes as well). Very rarely do they ever allow for contour shapes or custom finishing colors (now they might match the color of the edge with the predominate design color, but rarely do you have an option for the color of your choice).
Then you have to think about what type of edging do you want (usually determined by quantity or pay higher fee). Merrowed (typically requires a minimum, lowest I've ever known is 25, average is 50 count) or satin stitch. Satin would need to be finished off with either a laser or hot knife (again dependant on quantity).
Of course, if you are going stock shapes (rockers, circles etc), could always get pre-done patches and just have someone embroidered those locally.
The biggest thing, is the patch production itself. That's what gets people.
