Try not to bump a topic unless it has fallen off of the first page of the board (which in this board can take days), unnecessary bumps can be considered spam. In particular it can be counterproductive here since it can make it look like someone has already answered your question because there are several posts on the thread. It just makes it less likely that people will check the thread.
How do you plan on using these images? If you just need them for personal use, you wouldn't necessarily need to post them. Just save them and they will always be available in your saved drawings list, which you could access at any time.
If you just need to grab the image code, you could finish the image, then take a screenshot instead of posting it. This is something I've seen a lot in adoptable oekakis for things like info sheets, they make the sheet on the oekaki, but then screenshot it instead of posting it, cause they just need the image, not a whole oekaki thread. There are some nice screenshot apps you can download for your browser or computer if you don't like using the print screen button and manipulating it. Both Windows PCs and Macs come with one build in.
If it absolutely must be posted, I'd say Sketches and experiments would probably be best, its sort of a misc category. If you'd like an absolute answer on that though, I'd suggest sending in a
help ticket to ask, oekaki mods may have a better idea on a spot.