Keep it as basic as can be.
I mean take a look at real patches... The big red one, 2nd ID, 1st ID, 20th ENG, 101 airborne.
They all have very well known patches, but they are all very simple. Just need something like that, nothing to fancy, or it just looks like an ink blot.
And if it is just a symbol or something of the like, then you will have people ask you what it is, or what it means. Then you can tell them about the site and get them on.