A great way I've found to build pixel art, aside from Googling "Minecraft Ideas" is to look up Perler Beads and Sprites or Sprite Sheets. Sprite Sheets can be tricky to work with sometimes since the images are so small and get blurry upon zooming in. Perler Bead plans are GREAT though!! The images are usually high quality and you can really tell how many blocks to use since each bead represents a block or pixel and they're easy to see even with low quality images.
Another thing I've been doing is taking like-colored blocks and stacking 2x3 blocks on top of each other, using them kind of like a painter's pallette on the map. Lmmortal-Being/Dtart- has really opened my eyes to tons of ideas when it comes to building pixel art. Thanks Dtart-! And if anyone reads this and is a builder, good luck and have fun!