Yesterday I painted some bubble wrap and "stamped" on my watercolor background. I could have used a wee bit more paint but I like that the actual texture on the bubbles printed (and no messy paint "blurps"). So far so good: applying the acrylic very gently didn't disturb the watercolor at all and it added some interesting texture.
The whole point of this exercise was to see if I could paint a background with watercolor and acrylic, then run it through the inkjet printer, and this is where I'm less pleased with the results. After the acrylic dried, I used a foam brush to apply a layer of inkAID semi-gloss precoat (as directed in Digital Art Studio by Schminke, Krause and Lhotka). The inkAID is fairly viscous, and the watercolor smeared when I tried to even out the layer. When I didn't try to even out precoat layer, it dried very glossy in spots. The paper was quite bowed when it dried, so I let it sit overnight underneath a large weighted marble tile.
My test print was created in Photoshop using a few digital brushes. The butterfly, dragonfly and plant images were stamped at 100% opacity, while the two water spots were done at 65% opacity and flow. I wasn't sure how my little Canon printer would handle 140-lb watercolor paper (especially with a little residual curl), but it printed quite nicely. The print head caught the edges a wee bit, but trimming 1/8" from each side would take care of that.
It was an interesting experiment -- I loved painting the watercolor background and am so glad I scanned it before messing around more. I'm looking forward to making and scanning more of those and incorporating them into digital textures. Once the background is done and it is time to add digital stamps and/or images, I'd either do it all in Photoshop and print on photofabric (EQ Printables), or print the background and then use a digital ground on a sheer fabric to create an overlay. I haven't tried inkAID on fabric yet, but I'm leaning toward Golden Digital Ground because I think it would preserve the hand of the fabric much better (it isn't as gooey).
I hope that was interesting and useful. Wishing you a wonderful weekend of art!