Hmmm... This merit system seems a little bit unfair. I've been a Jr. User for quite some time now, but since I've not been posting much lately, I haven't received any merit. So... Now my rank has set back to Newbie. That's a little bit painfull, because now my images in threads I've started aren't showing any more.
So, I think I need to post some new quality posts fast to earn my merit.

Well, life isn't fair! However not having a high rank when you're not being active sounds pretty fair to me!

But you have one very good point in your post... there are many accounts which were created just to post an [ANN] thread by a team and were not active afterwards, those accounts probably have 0 merit so their images will be hidden after the last change.
Ofcourse main accounts exchanged merit with alt accounts to overcome this issue, but this beats the whole point of the 1 merit requirement.
In the future, if more changes like that happen, I wish to see a differentiation of image blocking and signature blocking. One of the problems with the spam in the forums is the signature farming, the image posting isn't an issue as far as I know. Let's not damage fair use of the forums along the cancerous part.