r.patch - Creates a composite raster map layer by using known category values from one (or more) map layer(s) to fill in areas of "no data" in another map layer
i.image.mosaic (script, not module; no man page) - script to mosaic (aerial) images. A new image will be created with extended colormap.
r.mapcalc - Raster map layer data calculator
r.combine - Allows category values from several raster map layers to be combined
v.patch - Creates a new binary vector map layer by combining other binary vector map layers
v.cutter - Polygon Cookie Cutter