I am making this painting available for greeting cards. The cards measure 5" x 7" and can be printed on either a matte or glossy finish card weight paper. You may order as a single card or a box of 10 (envelopes are included, of course). To order or see an image of the card, please go to the following web address: http://www.cafepress.com/helencread
The individual card is marked at $3.24, while a box of 10 is $18.49, plus shipping.
The company that handles the printing and shipment of the cards is called CafePress, and they have a good reputation from my research. The good thing about this, as an artist, is that there are no upfront costs (which is difficult for artists). In fact, that fact makes this new idea possible! So, we'll see how it goes.
My suggestion, I think, is to go with the matte finish paper, which even so will have a very slight shine to it.