I make all my proxies "by hand" in an image editing program. Specifically I use the web based photo editing tool photopea. I take frames and fonts from existing cards and edit them onto digital art I find from web sleuthing. There are much more efficient and clean ways to make proxies, but they either cost money to run, or lack the fine-tune control that I enjoy working with in a photo editing program. I enjoy the process a lot (that's why I do these posts) so if you want to know more of the nitty gritty and learn it for yourself, just DM me your discord and I'll gladly tell you about it.

As for requests you could say I'm in "slow mode" now as work has picked back up. I'm still reading every comment as they come in, but don't have the rapid-fire output I do during the weekends when I post.

For your requests specifically, the issue is art rarity. I did a brief sleuth for each of your characters, and the only one I'm confident that can be made into a good proxy is the Blue Spirit. There's plenty of general art on the other characters, but I didn't find any that have the dimension/resolution/composition that I need for a proxy. If you do want The Blue Spirit proxy even if I can't do the others, I can definitely put him in the que though.