Where do I submit to if I'm not sure?

The best thing in this case would be to look through a section you think it may come under and see if the images in that particular section fall under the same as the image you wish to submit. If not then try another section. Images submitted to the incorrect sections will be removed from the server without warning if they are found. You could also, submit the image to your Scraps, and then ask someone if they could possibly take a look at it and inform you of its correct section, then you can simply edit the file and move it.