What is a good method for wireless transmission of images in a ~2km radius?
Maybe some 900 Mhz modules if that is allowed.
The receiver needs at least 70 kb/s of bitrate if there is only one channel.
Lora has 5 kb/s, at the low range mode.

Based on your specs I'd wait around for Starlink and see that's going to cost you. Current Iridium is not very affordable.

I think the only license free option for these data-rates is WiFi, if DFS regulations can be followed. You can get sub $50 long range wifi gear from mikrotik. You'd need to beef up your battery design, since they will need some power. And you probably need a dish. 

The other option is to setup you own WISP with cellular modems. But you'd need licensing for that, if possible at all.

Maybe something lower power is possible if you are able to make a mesh network where you can scatter a few extra repeater nodes around.