at any rate…yes, you can needle-felt one piece to another – with a caveat. you know how something felted progresses from being a little bit felted, to more and more, eventually getting very hard and tight and hitting its felting limit? trying to attach something that is already near it felting limit will be hell, so work with pieces that aren't too felted. if the materials you already have to work with aren't joining well, try again with something less felt-y. make sense? also, the type of wool will make a different with needle felting just as it does with wet felting. needle felting can work on lots of fibers, it just depends on your patience and using good needles.

I agree – so many ideas for Christmas ornaments!

Re your question about felting fabric on fabric – am sure it must work – remember the gorgeous jacket on display at the Pendleton Store – the flowers on the pockets were all felted on using other wool fabrics. So beautiful!

As for your question: to the best of my knowledge, you can use the needle to attach anything felt-y to anything else felt-y. Biggest requirement: Patience.

As you mentioned, it does take time. Also, not an activity to do distracted — keep your eyes on the needle! (I speak from experience, here.)