what about a black and white design for the sheets? Here's a link to some (not all of them are only black and white...)
http://www.babybedding.com/crib-bedding-sheets?t=black

Or a white sheet and design for the crib skirt?

Cute sign. I have no recommendations but I love the sign.

SwaddleDesigns Muslin Fitted Crib Sheet, Hedgehogs Black https://www.amazon.com/dp/B01NGULBOV/ref=cm_sw_r_cp_api_5RnPybECPJ7RF

Muslin Baby Swaddle Blankets, 48x48 (3 Pack) Black, White, XO, Stripe, Cross https://www.amazon.com/dp/B01J6ZTZ3M/ref=cm_sw_r_cp_api_KSnPybR100T40

Kadut Kids Crib Sheet Set- 1 Pack - 100% Soft Muslin Cotton - Fitted Bed Sheets - Midnight Magic Blue - Easy Care, Machine washable - Fits Standard Crib Mattresses - Measures 28" x 52" x 9" https://www.amazon.com/dp/B01LX0H3FZ/ref=cm_sw_r_cp_api_cTnPybH1B32WW


I LOVE the Muslim sheets and swaddle blankets. That's all I use with my kiddos. But, I wouldn't be opposed to putting in some color. I could see some bright orange with the mix of black and white.

Congratulations on your expected baby boy! His room is going to look first-rate. That wood wall, the sign--excellent choices. I think you're spot-on to let his toys and books add color. Although you don't show a window wall, a Roman shade that completely blocks the light for bedtime would look good, maybe with an accent color stripe on either side. Do you have a rocker? A bookcase? One of those could be in the same accent color, too. Have fun with your little guy. I think he's going to love his room.

Great choices so far! I would get a black and white crib sheet.

I would also recommend white crib bedding! We have some that you may like :)