I remember at one point the quality of the photos used to be much higher. It's been quite some time since I've used this plugin but they seem very pixelated now. I have the image size set to 10mb even but no difference in quality.
https://steamcommunity.com/sharedfiles/filedetails/?id=2594909529
Sign Quality?
The quality of images is generally based on your client graphic settings.
I'm not sure, this looks like they're being way scaled down and then sized back up to fit the frame. The image looks the same on my macbook running minimal settings as it does on my PC with the 3090 and settings maxed. I'll double check though just to make sure.