I get a boner looking at graphics like this, and always have. I loved doing isometric sketches on grid paper, but never became any good at it.

Does anyone know good books for learning mosaic art?

Amazing tool! Thanks for pointing that out. Nice how it combines pixels and geometric shapes together in one tool, and supports mixing and combining all kinds of grids and pixels, even random Voronoi cells! It's on sale for only 8 EUR on Steam so I'll give it a try, since it looks so fun. The right-click pie menus was worth the price of admission!

At the opposite end of the abstraction spectrum from "Pixel Art" is Bert Monroy's amazing hyper-resolution photo-realistic art. He combines Illustrator together with Photoshop, ping-ponging back and forth between both tools. He's taught many classes and produced lots of videos showing how he works and teaching the tools he uses.

Times Square – On display at the Make Software Change the World Exhibit at the Computer History Museum, Mountain View, CA:

This is the largest image I have ever created, pushing the boundaries of the software and hardware as far as they can go. It was unveiled at the Photo Plus Expo in New York on October 28, 2010 as a work in progress. A 25 foot light box was constructed to display the piece that has been printed on a new material being introduced by Epson.

• The image size is 60 inches by 300 inches.

• The flattened file weighs in at 6.52 Gigabytes.

• It took four years to create.

• The painting is comprised of almost fifteen thousand individual Photoshop and Illustrator files.

• Taking a cumulative total of all the files, the overall image contains over 700,000 layers.

http://www.bertmonroy.com/timessquare/timessquare.html

Bert Monroy, Photoshop Artist

Photoshop Hall of Famer Bert Monroy talks about creating his largest piece to date “Times Square.” At 6.52 gigapixels, “Times Square” contains over 750,000 layers and depicts dozens of digital imaging artists and pioneers, as well as Monroy’s family and friends. This clip is from a full-length interview, conducted for CHM's upcoming exhibition, “Make Software: Change the World!,” opening January 28, 2017. Don’t miss your chance to see “Times Square” on display in “Make Software.”

https://www.youtube.com/watch?v=9JVgBWCPlFQ

Amsterdam Mist (2014):

My Amsterdam Mist is the culmination of twenty-two months of work. Every element in the image was meticulously created pixel-by-pixel using Adobe® Photoshop® and Adobe® Illustrator®. It is the first piece to be inspired by the shot rather than the scene itself.

http://www.bertmonroy.com/amsterdammist/amsterdammist.html

I’m not sure I’d call Times Square photorealistic, a lot of those people really scream “I was edited in and my lighting has nothing to do with the setting” to my eyes.