Getting back to the subject of thumbnails, gallery images, and banning...

First, although it may sound harsh: if you don't like Renderosity's rules, post somewhere else. Personally, I like DeviantArt: they don't require a thumbnail, so you can post an image without worrying if the thumbnail will be "bad".

Second, I don't think the original poster is saying the rules don't apply to him. Like many other artists, I think he's questioning why the nudity-rule applies to an image which he thinks doesn't have any nudity in it.
To use a previous example, it would be like walking into a house with a "no cigarettes" rule but carrying a cigarette box in your purse. The rule is obviously in place because the people in the house don't want smoking, but they still tell the visitor with the cigarette box to get out, even though the visitor wouldn't be smoking in their house.

I had a similar issue with an image back in February: the figure was clothed in lingerie, but someone, somehow could sort-of see nudity through the clothing. By my calculation, the "nudity" in the thumbnail was probably around 10 pixels in size. But, again, rules are rules and I shouldn't have uploaded a thumbnail with nudity.
My image was flagged, I was told to upload a new thumbnail image, and that a mark would be placed on my member record.

Although people may not get banned for accidentally posting a thumbnail with nudity, I've always wondered how many "marks" it takes to get banned. I've been a member here for literally 10 years (I joined in March 2000), so I sometimes wonder if all of my "marks" will eventually add up.
Will the "bad thumbnail" I posted in 2001 still count against me? What about a "bad forum post" I may have posted in 2002? Maybe the image I posted in 2010 will be enough to finally get me banned.

Seriously, though, I sometimes wonder if posting artistic nude images is even worth risking a "mark". Since February, I've made sure that none of my gallery images even come to showing any kind of nudity: the figures are either fully clothed or the image is a head-shot/ portrait.

VanishingPoint... Advanced 3D Modeling Solutions