just to update you, I took on board the comments about the babyish look and given the horrifying cost of curtains, I wouldn't want to be changing them any time soon so I ordered a Clarke and Clarke fabric with boats on it for the large window and a roman blind in the matching stripe fabric for the window opposite
I'd agree with Happy. My DS is almost 6 and thinks that all the younger ones linked to in this thread are "babyish" (quote)
For large windows/doors I'd go for stripes. I'm just about to order this Annie Sloan stripe fabric for our playroom, mostly because it's extra wide so less work involved (I make my own blinds & curtains)
I wouldn't be keen to spend hundreds on (albeit beautiful) younger fabric that they'll scoff at/ their "friends" will scoff at in a few years time!
How big is your window, and are you having linings, and will you need made to measure?
I ask as the total cost of your curtains may make you lean towards having something that suits that DC at the ages they are now, or whether you need something that they will not outgrow as quickly.
We have an enormous bay window in our playroom with really high ceilings, and it is more of a living room really than a playroom. I needed 28 metres of fabric for the curtains, plus lining, and had to have them made to measure. So I have chosen something that is grown up.
DS (5yo) has a 10 foot wide window in his bedroom, and I chose a fabric that will last him until he leaves home, as there is no way that I am having made to measure curtains plus linings for his window made on a regular basis. Take a look at Thread And Loop - they will send you samples. I went with Sandbanks - Brownsea (a strip with blues, greens, reads, beiges and creams) as I know that will last him well. I am really pleased with it.
I personally favour bright colours for a playroom, are you going for that or more muted New England GLTC type look? I wouldn't worry overly with matching to the walls, skimming stone is an excellent neutral - it's a taupe base so just be a bit careful with sand/cream tones in the curtains. If it's just part of a pattern it probably wouldn't matter I don't think. Get fabric samples before you commit!
The Harlequin fabric is very nice. How about having a roman blind made up instead? That way you use less fabric and it wont matter when you want to change it a few years down the line. Also looks a bit simpler than curtains, which might work well in a playroom where there are invariably lots of colours/toys/random bits of stuff!