@jacob.small I might be a hard ass about it, but I would recommend that we either answer the OP’s question, flag it as inappropriate or simply refrain from answering.
Now, I would second your opinion about the fact that this was already answered before. Here’s a link to one such thread: Is it possible? This explains how to import images into Revit, and place them in drafting views if I am not mistaken.
@jacob.small I guess I am saying that if you say “this was already answered”, at least post a link to it.
The second part of the question, which asks about using an image as a “decal” on a wall/floor is a little trickier. Technically OP is asking if its possible to import and image, and use it as a material on a wall/floor. From top of my head, that should be possible, but you would have to create a material, and assign it to the appropriate face. These methods are available in the API so it should be possible. I won’t recommend that route, because I don’t know enough about what the OP intends to do with such workflow.
That second workflow would require some custom programming. You can get an idea how to create a material from here: https://forums.autodesk.com/t5/revit-api-forum/create-new-material-and-add-new-physical-and-thermal-assets-with/td-p/7308186
I think that the easiest way to assign a material to Wall’s face might be the Paint method: http://www.revitapidocs.com/2018.1/f59f8872-e8d7-5d00-0e8c-44a36a843861.htm
Again, the above is quite involved, and no guarantee that the result will be what OP wants. @ssean7240