I'm working through a problem that I can't imagine is wholly unique but I haven't found a good solution to. I'd like to create a set of 50+ image targets that all appear similar enough to not be memorably distinctive to a human eye, but can all function as distinct targets within Vuforia. 

I started by using QR codes, but I've found once you reach a certain volume of trackers, they are too close to each other to function accurately. Any other thoughts? I've started manually modifying QR codes to make them more distinctive, but it's a pretty labor (and trial and error) intensive process. 

Thanks in advance!