I use paint. Just use the magnifying glass to zoom and press ctrl+g to get a grid. Although your picture is doable, Id recommend G/S/C sprites for the first two generations of pokemon. It migjt not seem like it, but that Blastoise is composed of several shades of colours (probably more than 5 types of blue etc) which will force you to ignore some colours because you dont have the right blocks for it.

Here is the link to the G/S/C sprites: http://www.spriters-resource.com/gameboy/pokegs/  

R/B/Y is even easier, but most of the sprites are ugly (imo)

Good luck!

Now you have 3 ways - photoshop, paint, or photobucket. Get your sprite, zoom in, and make a grid, then build and gain some rep in World of Minecraft : Realms. I'll also give you a /like with my 25 like power.

Go into photoshop, like before, but filter - pixelate - mossaic. Then select what you want.

Here is what I've made offline.

one other easy way is just to search a pixel art on the web. For easy ways just find a simple one. hoped this helped P.S. my pixel art is done!! its a panda!!!

ive made a mario and link pixel art, by googling the sprite i want, then went into paint and drew lines on it and gridded it out, then have both windows open at the same time, and add each layer 1 by 1