Perhaps the manufacturer of the drapes also has coordinating bedding? You don;t want a lot of pattern competing with the wallpaper accent. NO to buffalo check.

Pick one of the colors in the wallpaper and go with that. Grey drapes sounds drab, but

we cannot see them. You have so many options - go shopping and see what you like.

I would choose either the color of the wallpaper (creamy white) or one of the colors of the flowers.

Look for a matelasse bedspread in either the background color or one of the other colors in the wallpaper. Get some pillows that pick up the other colors using small overall pattern.

Here's an example There are lots more depending what you like.

And here are some pillow examples. Notice you can mix a small overall print with that wallpaper or a stripe, or a texture.

Pillow 1

Pillow 2

Pillow 3

Pillow 4

That's a large scale print. If you want a print on your bedding choose a color within the paper and find a much smaller motif (checks or stripes maybe) that uses it. I'd suggest a print with max of two colors. I'd have one of those colors similar to the paper's background white. That will make for less contrast between bed and wall.

I love the idea of a matelasse bedspread/coverlet, maybe in the blue of the wallpaper.

Or going with a small scale print, a one-color block print in blue or green.

The Company Store always has nice matelasse bedspreads/coverlets,

https://www.thecompanystore.com/quilts-coverlets/chaplin-matelasse-bedding-collection/c2a6-ps-a15.html

I'm more fearless than most when it comes to pattern and color, so here are some other options I would consider,

Pottery Barn's Rhett Check in blue, which is a fairly small check,

https://www.potterybarn.com/products/washed-check-print-duvet-sham-blue/?_br_psugg_q=rhett+check+organic+duvet+cover

PB Lila Reversible in blue multi,

https://www.potterybarn.com/products/lila-reversible-duvet-cover/?pkey=cduvet-covers-shams&isx=0.0.12369

PB Wheaton Stripe (a very thin stripe) in navy,

https://www.potterybarn.com/products/wheaton-stripe-duvet-sham-navy/?_br_psugg_q=wheaton+stripe+bedding

I like that PB Wheaton Stripe with the wallpaper! Looks fresh.

Otherwise, I would go with the blue matelasse :)

It would be more helpful if we could see pictures of your whole room, including the type of bed and nightstands you have. The wallpaper is bold and should be the main focus in the room. When I design bedrooms, I tend to go for a soothing, relaxing space for rest. Since you have a bold wall, I'd go plain on the bedding perhaps just picking up one color from the accent wall in the duvet. Something like the hotel bedding collection at many places including Pottery Barn. https://www.potterybarn.com/products/grand-organic-duvet-cover/?pkey=cblue&isx=0.0.10920 - Or get a washed linen matelasse (not a bedspread) and shams something like this https://www.restorationhardware.com/catalog/product/product.jsp?productId=prod1730272&categoryId=cat7640020 - and add a few pillows in one of the colors you like in the wallpaper. It may be easier to find pillows to coordinate with one of the colors you love as opposed to a hotel duvet as the colors may not match. I have the washed Belgium linen coverlet from Restoration Hardware and love it. Do post more pics so we can really see what the whole room looks like.

Here are the colors I pulled from your wallpaper. Any of these could be accent colors for your room.

Here are some examples of bedding that might work for your room. All from Wayfair. I'm sure you get the idea. I can't imagine that the gray does anything to boost the appearance of your room.

To paraphrase your question "would a large gray buffalo check work?"...well I'd have to see it and the room to opine. How large? How gray? What is the flooring,the headboard,the mood? I do think that with such a lovely paper, and the solid drapes, a print,stripe, or obvious texture is in order. Lots of ways to approach this....

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Now, myself? I would look at working soft coral shades into the mix with that paper and gray velvet drapes.

Start with a white or off-white duvet. Then find pillows and a coverlet in any of the colours pulled from the wallpaper. That should be easier to do than trying to find a colourful duvet to match.

So many options. Looking forward to see what you choose.

following

I love the fresh look of a check, such as this one suggested by beckysharp:

I think something along these lines could be quite lovely, combined with accent pillows to bring in some more of the wallpaper's hues.

Just to give you an idea of what I had in mind. Start with white/off-white. Then add accents in one or more colors from the wallpaper. Make sure to add different textures.

Go for the pink. : ) and a teensy dab of gray. Especially given the gray at the window. Pine Cone Hill.

I vote for the Wheaton pin stripe.

^ I really like that one, too!

^It looks beautiful Manon.

I'm always happy to help people spend money, especially on pretty bedding : ) .

And I love to see a lively, colorful room.

following....so I can see the room when your done!

Im NJ too!

Not a Pro.

Just throwing some ideas out there. ........

You mentioned you had dark gray velvet drapes that you wanted to leave in the room. I would probably get a solid color comforter and add velvet accent pillows to the bedding. Maybe have gray velvet shams made up to put up against the headboard to bring that color over to the bed. A gray throw to the end of the bed.

Easy peasy to do even if you don't sew. Just buy another panel of drape and give your tailor the pillows you need covered and they will usually make them up for you. Of course all it takes is $ :-)