Bamboo placemats popped into my head too. Don't they also make bamboo mats for floors in a similar way.
As you pointed out, you need to make sure whatever you do is secure and not slippery.
I like @MattiThundrrr 's idea of a surf style vintage stripe. You could do that with selective taping off and staining. It would also keep things from being to matchy to the point that they become monochromatic. Another option for the striping could be to find some antislip stair tread tape.
I never tried that lucid grip but I did lots of custom decks using colored aquarium sand, which is really artificial sand made like expanded glass. It comes in different colors.
I would embed that in some heavy coats of clear gloss acrylic paint and it made terrific grip. I did some boards like sand paintings, and some just had an overall coat of grip over wood grain.
If you do it like that, you can make any design you want. Tape it out on the board, spray paint, sprinkle the grip**, remove the tape.
**Some people say a salt shaker works really well for this but I never tried that
The other trick I used was to get some very course garnet sandpaper that was not waterproof and soak it until the garnets fell off. You have an arrangement of light to dark purple crystals that make excellent heavy duty grip.
I made some small adjustments then squared away the shop. A family member from Singapore is visiting and will do a video blog thing on my bike works. After I spent a couple hours getting the shop presentable, it was too hot for a test ride on Scurf. It's like a steam bath outside. I'll give it another try tomorrow morning. The wife has to help get the thing up the steps, it's 76" long and weighs 41 pounds.
That one rear brake probably won't be enough to stop the thing, but that's what the big bell is for, while I yell "Get out of the way!" Maybe I can sneak in this race, just a hundred miles north of here.
The film crew was out today for an interview and wanted to take some pics out in the street. They were amazed at how much these bikes weigh. I took advantage of the free help and did a test on the Scurf before the rain started back in. It did fine, I'm happy with it. All I need now is some sun for some photos.