There are old systems and the more progressive. Look at XNXX forum ( for example) regardless what you post, the site automatically reduces the size and you need to click on the image to make it bigger. Unforunately there are a lot of " bottom feeders" who still worry about bandwidth and the size of home screens and did not upgrade their " free" software. Fuck them.
One of the oldies is for example Literotica which allows only 100 kb image... Go figure
They still " live" in the 90ties ;)