Yes, I custom designed a mock Roman shade for my mother based on a totally function Roman shade that I made for myself (see 4th pic below). She loved the way it looked pulled up, so here are pictures: Not yet installed, still lying on the floor (approx. 16" long): Sorry for the poor lighting where it was installed. It is hanging about 8" higher than the window frame, barely covering the top moulding: Another one for my mother in a different room and different fabric: This was the her inspiration shade which is a fully functional Roman shade covering a window about 65" tall and 29" wide frame to frame: I used Simplicity pattern #9986, but had to adjust for a smaller width and longer length. You could also Google "mock roman shade" to see other styles. It will depend on the ACTUAL shade you choose and then design one to match how it looks pulled up.

I like the yellow you have, but your artwork has more blues in it. If you're keeping the rug maybe pull a blue or teal from that to inspire paint color. As for window treatments I'd do sheer light curtains, nothing too heavy since you already have heavier furniture and you don't want to take away from the beautiful molding and wainscoting.

Hunter Douglas makes a couple different shade product lines that come in co-ordinating fabrics/colors in both a horizontal and vertical version. These vertical options are not going to be the traditional PVC clanky, vertical blinds most are used to. You can get soft shades like Duette® Honeycombs, Skyline® Gliding Panels, or Luminette® Privacy Sheers. All these vertical products come in a horizontal version as well. Check out more at Hunter Douglas.

IMO the darker drape does not work with the sofa. As for snarkey I will say that to have blinds to keep out the sun is the worst choice I like to be able to see out of my windows so I choose solar shades to control light and heat they also give you day time privacy and then I add drapes for nightime privacy . As for what to se for drapes I would need to see the whole space and no matter what you choose make sure they are the proper length