Somebody's unused Dumping Grounds.
Dumping Grounds or "File Storage", or the "File Dump" was introduced in January 2010 as a place where users could upload content in order to share with friends or to get feedback on before submitting a final version to one of the portals. Images as well as Flash creations can be submitted to the Dumping Grounds. As explained in the FAQ, it is not intended to showcase material and the files can only be accessed by those it is made available to by the User.
The Dumping Grounds were described in the Newgrounds FAQ long before they were employed. Possibly, this was a reference to the NG Alpha system, which, before the 2007 redesign, allowed people to play unfinished Flash files uploaded by users. [1][2]
Limitations[]
Storage is limited to 512 MB for non-Supporters and 1 GB for Supporters. Starting in October 2022, it is a Supporter-only feature, though existing users were grandfathered.
File types accepted include: .fla, .swf, .bmp, .webp, .gif, .jpg, .png, .psd, .html, .rtf, .rar, .zip, and .tif. This includes a variety of Flash, image, and executable formats, but doesn't include any audio or video formats. Only registered Newgrounds users can use this feature. In a 2011 post Tom has promised a redesign including a bigger limitation for Dumping Grounds.