ok so i dug DEEP into google pictures and found old pictures, prototypes, inspiration, and more on yoshi. here are the sprites: yoshi happy: a basic picture of yoshi smiling :) yoshi shoeless: an old drawing of yoshi without his shoe on. yoshi mushroom unused: an unused sprite from the game Yoshi's Island. yoshi plane unused: an unused sprite from the game Yoshi's Island. yoshi prototype: a 16-bit pixel version of a prototype yoshi. yoshi ski unused: an unused sprite from the game Yoshi's Island. yoshi egg cracked: a sprite of a yoshi egg with cracks in it. YOSHI INSPIRATION: this is hard to explain, as there is so litle info about it, but I think this lil guy is from a very old game, and when nintendo wanted mario to ride something, they looked at this old sprite and took ideas from it. Again, i don't know if this is true. yoshi mario 64 ds: I think this is an ending scene from mario 64 ds. yoshi coin unused: an unused sprite from the game Yoshi's Island. yoshi concept art: the original drawing of yoshi, intended for Super Mario Bros., however, the game was not big enough to fit yoshi in,postponing his appearance until Super Mario World. you don't need to use all of these! i don't know if all of them directly relate to your project, but i hope you like them!
credit to google for the pictures, me for finding them, nintendo, and @GameYoshi