These are a number of individual small pieces put onto one large sheet for the sake of saving time uploading and to avoid spamming the gallery with a bunch of teeny-tiny pieces. Because they were composed individually, they weren't made together with a unified palette, and that number is likely the composite count of all the pieces together. Each individual pony is something like 12-16 colors, IIRC. Maybe a few more for ever-colorful Rainbow Dash.
Something inflated the color count to 144
Otherwise they look pretty good to me on a technical level. Just wanted to point the color issue out in case you're not aware.
27 px tall apiece (The forum I was making these for had a 27 px height max), variable width.
That's understandable.
I just mentioned it because your piece was in the queue at the time I commented.
Anyway, it got in. I can imagine them function very well in terms of forum useage.