I spent some time last night building a site for generating pot images: https://potimages.rknight.me/
You can choose from ~1000 icons (from the Font Awesome icon set), pick any colour you want for the background and download the image. You can also share your images with a link. e.g: https://potimages.rknight.me?i=dragon&ip=fas&c=f7f7f7&bg=EC5B5C
I hope this will be useful for a lot of people (I saw a lot of requests in the other thread so this might negate some of that).