Your wall looks quite blue on my monitor, but I'll trust your description of blue-grey. You can do a patterned curtain. Just make sure the scale of the pattern is either noticeably bigger or smaller than the rug pattern. I wouldn't do floral, though. You can pull a couple of colors from the rug to get your curtain colors, but try to not compete with the rug by adding too many different colors in the curtains. It's a cute rug, and should remain the focal point of your room!

One of my favorite looks right now is a small geometric, like lattice, checks, stripes, small 1" print, with a cream or white background. I think a print of reddish orange on cream would look great with the rug and the wall color. The fabrics below are from Romo and would make charming curtains if the tone is right with your rug. The scale and the one color on a white or cream background is my idea.