That sound spammy.... 
It's only spammy if your 28 posts are spam.
You've just got here, and you want to put pictures in announcements - that doesn't SOUND spammy,, that IS spammy.
You're really criticizing what people put in their Announcement thread? You might be jumping the shark, Jet.
To the OP, I think the Copper Membership is the best idea. But there is another way that won't cost you. You put the image link in your Announcement thread, and then rely on someone who is a Jr Member or senior to quote your image link. This will produce the image, in the post that contains the quote. It happens all the time.