Hi RedFiero88, first, welcome to Android Forums.
As far as blocking images from the Play store, that'd likely take a bit of work. The only way I can think to do it would be to modify the hosts file and add whatever domain google is using to host those pictures to it similar to this:
the only problem is, it'll likely cause all sorts of issues. Best case issues would be *no* (as in zero) images from that domain will load (likely includes all images not directly in the Play Store app file) and worse case would be that either the Play store would stop working all together (all data blocked) or worse worse would be no google at all.
Think of the errors!! Hmmm.... As I re-read this post, I notice that you already thought of all these host issues...
What about this ... if you installed all apps from a PC web browser using the web version of the play store... then you'd only get the apk sent your way, no images.
Or you could try one of those data monitor apps... I know a rom I was using several months ago had one built in...
Hey, I realize that my post was very little help, but I hope that either it helped a tiny bit or that someone else will come along who knows more.
Sorry I couldn't be more help, welcome to the site!