Upload an image to use as a floating background layer?

Is there an editor that allows uploading a non-georeferenced image, and gives the controls to manually place it in the background, so shapes can be traced over it? The example I’m trying to work on is a Condo complex that has recently finished construction, but all the aerial imagery isn’t updated yet to show that. I have the blueprints of the complex plan, including nearby roads, so if I were able to manually place that JPG as a ‘decal’ on the background, and adjust it so the nearby roads matched, I could trace the buildings off it to get a decent approximation of the building locations while waiting for satellite imagery to be updated.

I’m thinking with the increased usage of drones with downward-facing cameras (like the Parrot AR drone), this sort of use could see more usage for mapping areas missing satellite imagery. A drone with GPS could take off from a given known point, fly as high as it could and snap a picture and then come back down; you’d have a photo with only one fixed GPS point (center), but if a tool allowed placing it at that location and tweaking the scale, you could probably get some decent detail from it to trace, no?

There is a plugin to add an image layer, http://wiki.openstreetmap.org/wiki/JOSM/Plugins/PicLayer
You can resize, stretch and rotate to align it to the existing map layer and then use it as a background guide to add new features to the osm. You can also adjust the transparency so you can more easily see both the osm layer and your image.
You can do this another way by using the online web page Mapwarper to georeference an image and then add that to josm as a separate layer.
Both methods need a bit of practice to get proficient.

Thanks, that plugin works quite well! Mapwarper requires you to have permission to make the map public, which I don’t, though it’s a good thing to bear in mind for the future.

Do you have permission from the architect (or whoever has the copyright on the blueprints) to trace them for use in OSM ?

I am trying the same, but it seems that JPG as mentioned in the initial request is not supported. With what type(s) of file did you succeed?