Do you have an OpenGameArt account? It seems to me not because I tried to find it. OpenGameArt allow only free/libre assets. It is exactly what you do. Some people that search for free/libre assets avoid itch because here they need to apply more efforts to be sure it is free/libre... If I am right and you don't have an OGA account, I recommend you to create one. If you will create it, you will increase an auditory of people that see/use your art that can slightly increase number of donations... The platform is enough liberal to allow you place on page of each asset something like: "Check it on itch <link>" and "If you like it, you can donate <link to this page>"
P.S I can't find all my other comments so I decided to write you here because I will be 100% sure that I know where my comments...