Most single frames are 32x32 pixels, with jump being 32x64, and animations can range from 128x32, for idle which has 4 frames, to 608x64, for jump which has 19 frames. All of this information is found at https://blazingbeaks.com/mods/ and you can also download sprite_templates.zip which contains example character sprites and all of the necessary hitbox overlays.

Hope that helps.

what are the dimensions to create a character