Instead of paint, consider an opaque or semi-opaque stain for the deck, provided you can power wash off what's there. It penetrates the wood instead of sitting on top of it, therefore, it lasts longer. 12 x 12 is not a lot of space (I had a deck that size) so consider something that meets both your wants. If you do something like this, you can add 4 chairs around it and it serves a dual purpose.

https://www.wayfair.com/outdoor/pdp/endless-summer-duval-steel-propane-fire-pit-table-ed10011.html

You could also add posts to the corners of your deck and run lighting overhead. Outdoor lights like this have GFCI's built right in to run lights.

https://www.walmart.com/ip/Spence-1-Light-Outdoor-Wall-Lantern-With-Seeded-Glass-and-Built-In-GFCI-Outlets-Black-Finish/826317923?

Then add planters in varying heights to the corners filled with plants.

Few extra pics.