This page details my process for working with untagged images. Please make suggestions regarding its improvement on my talk page so that I can consider them.
I ask myself if the image will actually be used for the benefit of Wikipedia. If it looks like some dorky picture, something that was used for vandalism only, or something only used in an article about to be speedied, I just tag it with {{subst:nsd}} or {{subst:nld}} (no source deletion or nolicense deletion) depending on which applies.
If I can determine the appropriate license for the image myself, then I will go ahead and tag it. There is a pretty complete list of copyright tags at WP:IT. I get a lot of logos {{logo}}, albums {{albumcover}} and screenshots, which are usually something like {{tv-screenshot}} or {{video-screenshot}} (for video games). If it looks like a photograph that the user took themself, then I tag it with {{GFDL-presumed|Hetar}}. Normally self taken photos have a relatively large resolution, and often times they will have left a comment indicating that they took it in the edit summary. Most of the time its just a matter of picking a matching license from WP:IT, which gets easier after some practice.
Sources for pictures are pretty important, however if the image is some sort of a screenshot, box cover, logo, or poster, normally the source is obvious, so I try not to make a big deal of it.
Any image tagged with {{fairusein|articlename}} needs to have a fair use rationale provided. Normally this is just a couple of points that say this is fair use because no other images of it exist, its impossible to take another picture (ie, the building burned down or whatever), its of low resolution, etc. Images that don't have this rational can be tagged with {{subst:nrd}}.
I would also recommend reading WP:FU (no pun intended) as it can point out some interesting cases where images do not qualify for fair use. Other fair use review tags include {{fair use reduce}} {{fairusereview}} and {{fairusedisputed}}.
Ocassionally you may come across images that appear to have a bogus license. For example, I came across an image of a bycicle from a manufacturers webpage today that was tagged with {{norightsreserved}}. In some instances you may just want to retag these images with an appropriate fair use license, but remember, if it is reasonably possible for us to obtain another 'free' image of the same type then we reall shouldn't be using a fair use image. At any rate, images that have bogus licenses, or for which you dispute the license should be listed at WP:PUI with a short explanation of why the current license is invalid.
Fair use images that are not used in any articles should be tagged with {{subst:orfud}}.
Many users (new or otherwise) will upload an image and say something to the effect of "I talked to the author and they gave me permission to use it on Wikipedia" or, "They said we can use it as long as its not for commercial purposes." Both of these permissions are insufficient because we license our content to different entities (ex: answers.com) and in some cases the foundation makes money from these uses. Relevant tags for images like this are {{copyrighted}} and {{noncommercial}}.
Images with a fair use tag that is obviously invalid (ie a tag that claims fair use as currency when the image is of a magazine cover) are eligible for speedy deletion and can be tagged {{db-badfairuse}} Also, see Wikipedia:Criteria for speedy deletion#Images/Media.
