I have nor ticks skip in my cap, neither i'm encountering alpha-problems (at the moment using PNG24 (GIF also will do) instead of indexed and bad supported PNG8). I have character with 4 animations 4 frames each.
But, I'm working with pixel art, so every single frame is 48x48 px. 96x48 in some places.
Here's how i do it in the game i'm working on now (just for proof of concept)
There are 3 loops, by anim name, angle and frame. "Character" is a family of objects.
And here are the functions for converting anim number to name