Raster imagery is useless crap? Wow, I didn't know that.
I would agree that Garmin places too many limitations on their implementation, the new devices can handle a maximum of 500 tiles at 1024x1024 pixels but older units can only handle 100 tiles. And the screens on my Oregon and Montana really leave a lot to be desired when viewing a dense image (maybe the Oregon 6xx and Monterra screens are better?).
I created raster imagery at 10 feet/pixel of the southern half of New Jersey by mapping aerial orthophotography onto NED 1/9 arc second LIDAR DEM. To make it as compatible as possible with Garmin's limits, I broke it into a total of 64 individual USGS quads that each contain 25 tiles. So users of older devices can load 4 USGS quads at a time and new devices can load 20 quads at a time.
Basecamp doesn't have any restrictions on size so you can load the whole dataset there, or you can use Google Earth or any other software that opens .kmz files. Have not posted it here (I wouldn't want to add to the "useless crap" that's already here). I offer a direct download from my own site and it has been very well received by people in the area since it's a rather unique map.
I also have a .rmap version that works on both iOS and android apps (which don't have Garmin's limitations). More info and download link here:
https://forums.njpinebarrens.com/threads/lidar-enhanced-aerial-views.10340/page-3#post-124283