Hello and I love this post! My goal in decorating any space is unexpected details in unexpected places, so I love that you are considering artwork for your laundy room! First off, I love the color you selected. Seriously, can you go wrong with that inky gray-blue color? The answer is no, you cannot.
I have two thoughts on you art choice, with accessories to go with either decision (of course). I like the first option - the Keep Calm and Wash On - because it is a cheeky nod to the original poster that was Everywhere for a long time. And I agree - black background with white letters. And if you go with that option, here are some ideas for storage containers, both from Target.
The Target Trend Lab Versailles Fabric Storage Bin Set:
Or the Target Tote with Eyelet Handles:
I'm also torn because that limits you to only black, white and the wall color. You could always tie bright yellow ribbon to the handles on the second option or do some kind of colorful tags to label the contents of each container. I also like the idea of a washed-out photograph, especially something that's personal to you. If you go with that option, then I like the idea of some industrial-looking metal containers.
The Container Store Silver Mesh Handy Bin (great for a laundry room and sorting all your loads...plus it has wheels!):
The Container Store Platinum Elfa Drawers (assuming there is shelving):
And, for whatever you choose, I love it when people use jars like these to hold their detergent or other laundry accessories. From Target, natch:
Obviously if you use liquid detergent this doesn't really work, but I use Borax in addition to my liquid detergent, and if I had the space (see below), I would totally store it in a pretty container.
And lastly, a picture of my laundry closet. The pails are from Ikea and I love them.