This user has definitively stopped contributing on 2014-7-30
All Natubes images uploaded untill then (and being made by Nicolas Pleumekers), are on: http://commons.wikimedia.org/wiki/Special:ListFiles/Natubes
This user's images are uploaded here under the "Creative Commons Attribution-Share Alike 3.0 Unported license". This licence says among others:"You must attribute the work in the manner specified by the author or licensor".
The relevant specification by the author in this case is the one as follows:
Users of one or more of these images must quote in a usual way the sentence:
"Image made by nature protector Natubico; www.vivism.info"
In case one wants to use images without having to attribute it in this manner, one can contact the author via: email@example.com.