I think it depends upon the room, wall color, window size and the fabrics involved. I generally like the darker on the bottom and lighter on the top, but I have a hard time envisioning a print on the bottom unless it is 2/3 of the total length. So with no more information, I would say put the print on the top, either a wide band like 24" or 2/3 of the length of the whole drape.
Diane

I've seen all kinds of combinations and when the scale is right it looks great. Don't ask me what the right scale is, though! You'll probably get more feedback if you repost this and put more info in the title, like - Combining print with solid for curtains - Scale? Then people who don't sew won't think that's what you're looking for - I thought this was a sewing question based on your title.

You also might try to post this on the sewing forum.

I love to sew and have made many window treatments in my day, but none with a combo of solid and print. Here's a picture, taken ages ago with my then 1.3MP cell phone camera so not the best and soon after we moved in pre trim work, of the WTs I made with three different fabrics...
{{!gwi}}