Since gen V came out, back sprites have changed dramatically, taking a full view from behind.
Some people prefere to stick to sprites in generation IV style (160x160 in 2x size).
The main purpose of this thread is to collect/create a resource of back sprites (but front sprites are welcome too!). The back sprites in Essentials, prior to gen V can be used as a reference for the style.
I created a Google Doc, with links to the sprites. If you are making a contribution, please start a new column with your name in it, so that we keep the doc organized.
Having the front sprites would be really nice too. I did not add them to the doc yet, but please, feel free to add them.
Indeed, I didn't see Victini's sprite. I'll add it right now.
The whole point of using the google doc is that you or anyone can edit it anytime. So adding something I didn't or updating the sprites is easier.