As an ex-Moderator, you are in a unique situation Ineke.
As a Mod, you had an unlimited attachment count.
Ideally, we don't want images being deleted from the Forum, as they go towards making a post more interesting and relevant. Imagine if a post said ... "Refer to the image of this shrimp ..." and the picture was gone because the owner had to delete it to recover space.
@Cesar is the site owner now. Hopefully he will chime in soon. I have not been a paid member for so long that I don't know if there is a limit or not. If I ever stopped being a Mod on this forum, I will face the same problem you have now. And hopefully, I won't have to go deleting my pictures, because a lot of my pictures are what makes my forum posts relevant.
If there is no way around it, you just have to come back as an SKFA Mod. ?