Thanks grumpntug, I indeed left the full res images (unmarked and for everyone to take for non commercial use) for comparable reasons flat_3d is bringing up.
So my initial take on this was to leave things to common sense (yeah, sounds strange).
For example this website (http://www.zmescience.com/science/neurology-science/neuron-database-06042015/) is also using one of the images (probably just downloaded the full res preview). But this is a different story, they put the image destination under it (good for me, CGt and this community in general). There is value in the use here, there also is no direct commercial gain in the way it is used (Would be an unnecessary time delay if the author of this article would have to contact me to ask for permissions).
This kind of use is something I can promote, it's an example that leaving a door open to common sense usages can work. The person in charge of writhing the Open-Access Neuron Database article may have reasoned that it's for an article related to an Open Source project, so it's just going to rout traffic and it will be ok when the source of the image is mentioned, he was probably also thinking the author of the image will be ok with this (and he would be right).
So the decision to mark the images and hinder common sense reasoning/use like this leaves me divided. In the meanwhile the user hoe was portraying/redistributing the images as free stock images quickly replayed to my request and kindly removed the images. He even removed the title free stock images in that gallery, so now the remaining images are also not advertised as free stock images anymore.
But all of this is actually a bit off topic, my real question was, is anyone ells interested in having a watermark option in the image upload area, and if so could CGt install such feature?