The result is a bit rough but I think it is good enough when seen at the final resolution of the game. I will make another attempt later this night or tomorrow with a larger texture. I will probably have to make an additional pass on a few models to improve them after seeing them in-game.
First, create a [very simple] model in Blender.
Second, create the seams (the colored edges) to prepare unwrapping.
Then, start the automatic unwrapping and manually arrange (scale/place) the various pieces.
After exporting the UV layout to an image, paint it in Gimp.
And back to Blender to see the result.
A few more models I did for the game...
The "crystal ball on a tripod"
The return of the pumpkin vengeance 2 (now, with a nose)
And an innocent animal found here for no reason...