Show everyone how your pixel chops have developped since you have started your Pixel Joint journey. Take the first artwork submitted to your gallery and do it all over again, but better.
I understand that someone's first artwork might be too difficult, too big, too time consuming for one week, or the opposite - it is not interesting or challenging enough. In that case it is allowed to choose the second one.
If you think that todays you would draw the same thing on a bigger or smaller canvas - change it for the better. If you find your past colour choices terrible - update the palette. If nowadays you are better at palette control - make it smaller. If it was a portrait of your boyfried, but you have a hotter boyfried now - draw the new one in a similar way. Anything from what this past artwork was capturing, that had changed for the better (no matter if it's your pixel skills or your topic choices), need to be reflected in this new version, but it still have to be obvious that this is a new approach at that past artwork and not a new, completely unrelated piece.
Also, if that piece was an entry to a challenge, and you would want to show a more impressive entry to that challenge with todays experience, than you have to follow the rules of that challenge.
Link the chosen (first or second) artwork in the description of your challenge entry, to make our lifes easier.
Canvas size: Exactly as your chosen artwork, or "better".
Colours: Exactly as your chosen artwork, or smaller.
Transparency: As your chosen artwork.
Animation: As your chosen artwork.
The challenge thread will have all the challenge updates. The thread is also a great place to post your WIPs.