multifandomdoodle

From:

Hello, thanks for asking!

Here is an assortment of resources with different people discussing how they post their fanart to AO3.

AO3 hosted tutorials:
-Embedding Media at the Archive Of Our Own (official admin post; if you scroll down to "Inserting Art" you'll see some image hosting suggestions from the AO3 admins, but you will also see that all the admins' image hosting examples have been noted "Caution" or "Not Recommended"... YMMV but I suggest looking into the resources below for image hosting guidance)
-Tutorial on putting pictures and gif on AO3
-...and if you're feeling really brave, How To Size Images on AO3 and How To Make Images Fit In Mobile Browsers

Other resources:
-How to post images within a story on AO3 (Dropbox hosting)
-How to post fanart on Archive Of Our Own (imgur hosting, deviantART hosting)
-Reliable Long-term Image Hosting Sites (list of image hosting sites, includes Discord)
-Any advice on adding fanart to your fanfic on AO3? (see comments)
-Discussion of image hosting, specifically on Discord
-Traditional artists discuss scanning, image hosting, and uploading to AO3

Please let me know if these links are helpful!