Yep, this is what I do for a living
Copper piping is an exellent idea for a drapery rod.
The hardware store is an underutilised place in the field of interior design I think. So rich in posibilities if a little imagination is used.
You could get a thick length of dowling too, or even a length of bamboo from the garden centre.
You can also use plumbing fixtures to attact the rod to the walls.
If you have a woodcraft section in your local hardward store you should be able to find wooden forms (egg shapes, ball shapes of various sizes etc.)that can be attached to the end of whatever you have decided to use for a pole with "No More Nails|", to act as finials and just jazz it up a bit.
In Canada these are usually no more than a couple of dollars each, even for the larger ones, so they would be very cheap in the US, same goes for the plumbing fixtures, although brackets should only be a few dollars each too.
Of course, if you use plumbing fixtures instead of brackets you'll have to take the whole thing off the wall to wash the curtains, so from a convenience point of view brackets are easier.
If you're sticking with the spongy pattern I would try to either find fabric, or perhaps ready made drapes in a shade close to one of the colours you've used on the wall.
My preference would be for the darker shade in general and without having seen the colours, but either would do.
You can easily change tab top curtains into pleated curtains if you'd prefer that look.
Just iron the tabs flat against the back of the curtain and in a matching thread sew a line across the the free end of each tab (anywhere along the tab willdo as long as you have left enough space to feed the rod back through), attaching it to the main body of the curtain.
Then simply thread the tabs onto the rod as normal and your tabs tops will have turned into loosely pleated curtains.
This will obviously make the curtains shorter and they may no longer touch the floor.
You might not mind that look, but if you don't like that, one very hot trend at the moment is to have your curtains edged in a contrasting or complimentary fabric.
Simply buy a couple of yards of fabric and sew a strip onto the bottom so your drapes touch the floor.
This fabric could be in whatever colour you have decided to use for accents in the room, or simply be a darker of lighter shade of your main curtain fabirc. The choice is really yours, so many options.