I would use a light tan of the background or a light green from the leaves.

Wanted a wallpapered feature wall too

The only wallpaper that will coordinate beautifully with colorful large patterned curtains is a small scale pattern or stripe from the same manufacturer. Such small scale patterns do not make good feature walls. Choose one star pattern per room, two will just fight each other.

I like your curtains, and they provide enough pattern without adding a wallpapered feature wall. For the wall color, choose a beige color that looks good with your carpet.

Beautiful drapes.

Definitely use a light tan as similar to the background of your drapes for your wall paint color as you can find (or lighter but not darker) and consider taking a drape panel with you to the paint store. Try to find a tan without any pink or yellow hue.

Definitely would not want wallpaper in this room. Much too likely that it would clash with those floral drapes.

You might use a non- floral (geomtric or striped) wallpaper trim tape at the top of your wall -- but in a different room -- for your wallpaper wall rather than adding wallpaper to an entire wall.

One wallpaper option might be to wallpaper the back wall of a bookshelf -- something much more easily removed from any room if you find it doesn't work well visually.

I agree that the paint needs to look good with the drapes, but I think it's even more important that it look good with the carpet, since there's a lot of carpet color and only a bit of drapery background color.

Need to see the rest of the room to get a sense of size, scale and proportion and to see the colors of the furniture.

I would do a pale green from the drapes for the wall color and no wallpaper, I have no idea what room this is to me the drpaes are too busy already .