So the https://masto-fe.superseriousbusiness.org frontend* turns out to have, as an alternative to attaching an image, a UI for just *drawing* a simple image, but either it doesn't work well, or the touchscreen on my Lenovo laptop turns out to be terrible for drawing, or both. Lines don't draw in ways I expect, in ways that seem hard to leverage as "stylized" limitations. I think it's the screen.

* (Which I've been using instead of doing free QA for the fundamentally-misconceived Mastodon 5 UI change)