Congratulations.

Is this basically meant as a low-res texture for Minecraft/Voxelibre?

A quick NES-demake (palette, 16x16 tiles and not more than black + 3 colors per tile) for no apparant reason.

Feedback from that edit:

• Your tile size is odd with 16x15px and only the last column also has a right border, which means it will not align with the other tiles.
• If it was meant as 15x14px with 1px spacing on all sides, then the last column is only 14x14x.
• Everybody who wants to use it with tiles of 2^n x 2^n has to edit or stretch them.
• Some tiles have color differences so minimal that I can barely see them on higher zoom (colum, row; starting with 0): 0,1; 2,1; 3,1; 4,1; 1,2
• The PNG usese 59 unique colors (irrelevant fun fact)

2,1 (the orange screen?) looks different from 3,1 and 4,1 like it was colorized with an color shift effect:

• the white is slightly orange while the other two have pure white
• the orange (#FF9E00) is slightly different from 2,2 and 3,4 (#FF9500)

Much of that is just my pixelart nitpickiness, but it slightly influences how well the PNG can be compressed. If colors are the same, the compression algorithm can utilize that, but if they only differ a bit they have to be treated as different colors. There are also tools that can reduce the size of PNGs to some extend. (Not really like they get used much here on OGA and I usually don't use them either) Here examples with standard settings of optipng, pngcrush and pngquant as well as my demake which has a de facto reduction in color but more pixels:$ ls -l costume*.png
-rw-r--r-- 1 user users  873 14. Nov 20:28 costume1_nes_demake.png
-rw-r--r-- 1 user users 1078 15. Nov 00:31 costume1optipng.png
-rw-r--r-- 1 user users 2037 14. Nov 20:04 costume1.png
-rw-r--r-- 1 user users 1205 15. Nov 00:30 costume1pngcrush.png
-rw-r--r-- 1 user users 1078 15. Nov 00:30 costume1pngquant.png
$ file costume*.png
costume1_nes_demake.png: PNG image data, 80 x 64, 8-bit colormap, non-interlaced
costume1optipng.png:     PNG image data, 80 x 61, 8-bit colormap, non-interlaced
costume1.png:            PNG image data, 80 x 61, 8-bit/color RGBA, non-interlaced
costume1pngcrush.png:    PNG image data, 80 x 61, 8-bit/color RGBA, non-interlaced
costume1pngquant.png:    PNG image data, 80 x 61, 8-bit colormap, non-interlacedThe numbers like 2037 are size in Bytes. That means costume1optipng.png is 53% the size of costume1.png. costume1_nes_demake.png only 43%   Not things you have to change, but just because you said it was your first ever.

Trying to use that <pre> totally didn't work.

I shouldn't have recommended pngquant, since it can be lossy.

But I forgot zopflipng which is way better with this, especially with extreme settings (zopflipng --iterations=500 --filters=01234mepb).

• Default: 996B (49%)
• Extreme: 993B
• Default (nes_demake): 741B (85% or 36% of original; loses transparency)
• Extreme (nes_demake): 740B
• Default (nes_demake converted to RGB): 768B (88% or 38% of original)
• Extreme (nes_demake converted to RGB): 767B

Zopfli can be very slow, but you won't notice it that much for small images.