I only see clothes for sale in your store. So far, no problem I can see there. As for usage, if you aren't reselling the actual images from 3D.sk as is and are not using them in pornography, IMHO, I think you are covered.

Their license clearly states (and it's also quoted on their homepage) "Licence guarantees that once you download the photos you can use them for any personal or commercial project as long as you wish without any additional payment." That covers money usage. They also state in the FAQ: "Yes, you can use all of our photos for commercial projects. So it's possible to create textures from our photos to map 3D characters and then sell the characters and/or textures to 3rd parties." It does state in the commercial license that they must be re-worked. Knowing their pictures, they always need re-working.

They go into lengthy, easy to understand details here for commercial use:
http://www.3d.sk/commercial-terms

The hobby license is similar but not as lengthy:
http://www.3d.sk/hobby-terms

"For clarity, you may not use the Content in products for resale, license or other distribution, unless the original Content has been fundamentally modified or transformed sufficiently that it constitutes an original work entitling the author or artist to copyright protection under applicable law, and where the primary value of such transformed or derivative work is not recognizable as the Content nor is the Content capable of being downloaded, extracted or accessed by a third party as a stand-alone file (satisfaction of these conditions will constitute the work as a “Permitted Derivative Work” for the purposes of this Agreement). "

"You may not use the Content in a fashion that is considered by 3D.sk (acting reasonably) as or under applicable law is considered pornographic, obscene, immoral, infringing, defamatory or libelous in nature;"

Porn is porn and is usually classified as obscene - it involves the use of - well you know. Soft core love scenes are not porn and have never been considered porn in western courts. R rated movies are not porn. So there you go.

They do ask that you contact them if you have questions. But I really don't think you have real worries, IMHO.