I suppose scrapped organisms technically go here. I sketch things that never get finished all the time, far too many to post, but I have a few with completed / mostly completed art too.
These ones are early versions of concepts that became submissions with different artwork later:

Fourmaw saucebacks were originally conceptualized as neotenous derivatives of the megatusk lineage. The main difference being only one terminating fang per jaw, matching juveniles of the lineage. Scrapped because I decided it wasn't very plausible, then reimagined the concept as a shrewback instead.

Originally, argusraptors were gonna just be the Terrible Argusraptor on its own rather than a species complex. I was never really satisfied with this art and I was later inspired by wolves and coyotes to broaden the scope of the submission.

Big-headed camoback wasn't exactly submitted later, but it's the same concept as the lunging camoback--slower ambush hunter more suited to its environment. Originally lost interest because it was too terran and I'd messed up the mouth anatomy and didn't want to fix it, interest regained when I realized I could give it stupidly long grasshopper hindquarters.
This one was cannibalized for a later species concept:

This is the athol. Its name was re-used as part of atholat later, but apart from the namesake lack of a dome the two species couldn't be any more different. This was meant to be a star-tongued gulper-esque insectivore native to Darwin, but I lost interest somewhere along the way. It could probably still work, but I don't feel like making it.
These ones don't really have anything like them existing at present:

The baresnout shrew was a descendant of the opportunity shrew, and one of my earliest species concepts as one can tell by the older art style. It was meant to be an aggressive scavenger of some sort, but it was designed with looks in mind over functionality. It could probably be reworked as a descendant of the stink shrew, but if I did that I'd probably completely redesign it and make new art.

Woah, a scrapped shrog! The fermi dwarfshrog was meant to be native to Fermi when it was still just a tiny unforgiving desert island. It's small and neotenous, and I had this idea that it could use a tiny descendant of bangsticks called "pistolsticks" as a sort of one-time use pistol. It actually has a fairly complete description, but I ended up losing interest in the pistolsticks (which was never drawn). Then I put off finishing or reworking it for so long that now Fermi's completely changed and it doesn't make sense anymore, lol.
(I had had an additional idea for a descendant of it that pretended to be a baby dockshrog for free food!)

Mittenlip was a stowaway harmbless descendant that became a full-time specialist of seafaring shrew food stores. Not really much to say about it, might still work but I don't feel like writing a new description.

Softback was a descendant of the glacial sauceback that was meant to be an aesthetical hollow echo of waxfaces. The teeth don't make any sense. It no longer serves any purpose.

Cephaler was meant to be a short-necked shrew that got even anatomically stupider. It has no neck, and the head and the shoulder girdle are one. Current stance: No.

Unnamed kehaida descendant. Decided it was too ugly.

Pop shrew, a weird bubbleskin that converged on more primitive shrews. Evolved too fast and rendered obsolete by the surprise return of soriparasites (which can do this more easily and more interestingly).