edit for the third time,
I'm wanting to upload my mature screenshots, but they are not a part of a mod, do i need to havee a supporter membership to upload Adult Screenshots?
Yes, you need a supporter membership to upload adult images to the Supporter's image share.
Fixed that for ya' Obliette!
The Terms of Service address this very issue. (And many others, so I suggest that anyone who hasn't read them completely takes the opportunity to do so. They're not very long, they are very well written, and there's a link on the top-right of every page.)
Relevant section from the ToS is:
Uploading to the Image Share section
The image share section of Nexus Sites was designed to allow players to share their favourite or informative screenshots of the games they play with other users of the site. While an adult-only tag is available that should be used if the image would be rated anything higher than a PG-13 in US/UK media we do not want images of nude characters hosted in the Image Share section. “No nudity” includes boobs and genitalia as well as visible pubic hair in the genitalia area.
Yes, there’s an adult-only content filter (that some have just taken to mean “nude content” filter) but adult-only content is more than just nudity. It’s excessive gore, it’s risque comic-strips, it’s pictures of characters wearing the skimpiest outfits possible without breaking the rules. It’s basically everything you wouldn’t want to have your boss catching you looking through at work.
For a more detailed look at what is and isn't acceptable within the Image Share section please read Robin's thread on the subject.
Aside from no nudity, you should only upload images that would be acceptable in the file database. This, importantly, means that you should not upload pictures of mods you are using that would not be allowed in the file database such as mods using ported or copyrighted content. Whether or not you use these mods is your choice, but please do not upload pictures of these mods in action to the Image Share section of the sites.
As of the 12th of May 2010 a private "Supporter" only Image Share section is available for Supporter members of the site. This section may contain images of all types within the legal bounds of the internet. That is to say that nudity is permitted but any images that wouldn't be legally acceptable (such as pictures of naked children, bestiality, necrophilia, copyrighted content etc.) are still not allowed.