Hmm, well, there's 4 main ways I can think of to add a cape. The first would be to add it as a hat and I'm not sure how well it would work without looking at the code, the second is to add it as a shirt, this would probably be the best, but the cape wouldn't go below the waist and would be paired ot a certain piece of armor, the third is to add it as pants, similar problems of it being tied to a piece of armor and only being below the waist. Lastly someone could add it in properly, which would be a super big pain to actually do as a mod (if it wasn't a mod it wouldn't be as big of a pain, but would still be a bit of work). There's a fifth way you might be able to do it, but that would probably end up not working very well.

Essentially, a full on cape would be very hard to put into the game as a mod. If you're ok with it being attatched to a piece of armor and only being above the waist then you can give a try to making a cape by modifying the top fourth of images in an armor set (the part with the main body of the armor) so that it includes a cape. Here's an armor piece I think would look pretty good with a cape if you want to try: https://imgur.com/Qzi4Odn

If you do this, post the edited image here and I'll turn it into a mod for you.

Also, Moving this to the modding section (called "Workshop Discussions") of the forums.

Can accessories appear on the character sprite? Also, thanks for the info.

well you could do it as a two piece shirt and pants.. also so that combined its a full cape but not sure how well that woudl work as a whole unless diffrent cape sets were made with diffrent armor properties or other atributes.. im not even sure if you could do it that way but it was an idea

Firstly, accessories would be annoying to put on the character sprite. Similarly to the cape, it could be done, but it would be an incredible pain to mod, and too much work to be worth it for the devs.

Secondly, for making both shirt and pants, I'm not sure that would work because I think the animations for the upper half of the body are mixed with the ones from the lower half, and as such I think it wold be impossible to keep the two halves of the cape synced.

The cape would almost be a 3 armor piece set to get the full effect while moving