Matching motifs on both sides - do you mirror them or make each one different?

I always do two different poses on cardigans and it's never once read as messy. I put a sleeping fox on the left chest of a green cardigan a couple years back and a standing one on the right, and people notice the pair and smile every time I wear it. Identical mirrored designs feel very store-bought to me, like something mass produced. The mismatch is the charm, especially with an animal like a possum that's naturally a bit chaotic anyway.

On the wet fabric question, I stitch corrections while it's still damp, always. Once I waited a full day to fix crooked whiskers on a cat design and the fabric had stiffened slightly in a different way, which made the needle drag and left visible holes around the new stitches. Damp fabric accepts the needle more like it did the first time. The one thing I do wait on is judging the design itself. Wet wash-away leftovers and drying ripples lie to your eyes, so I'll pin it flat on a towel and walk away, then come back the next morning before deciding anything is actually wrong.

For eyes specifically, off by a few millimeters is often the fabric pulling, not the stitching. Put on the garment, look in a mirror from a couple feet back, and see if it still bothers you at wearing distance. Embroidery gets judged way harder at close range than anyone will ever look at it in real life.

I'm on the other side of this one. I did a pair of goldfinches on a navy cardigan last winter, one mirrored copy on each side, and I actually think the symmetry is what makes it look deliberate. My reasoning came from a bad expirience, honestly. Years back I put two different flowers on a denim jacket and a coworker asked if I'd run out of the first pattern. That comment stuck with me and now I default to mirrored, especially on anything I might wear somewhere a bit dressier.

For the eyes, I've always waited until everything is bone dry before I judge anything. Damp stabilizer residue and rippled fabric lie to you badly. I ruined a heron's beak once by redoing it wet, then realized the original placement was fine once it flattened. Now I pin the piece to a blocking board overnight and look at it fresh in the morning with coffee before touching a single stitch. I do think a hanging possum could work if the pairing felt obviously intentional, like the two animals facing each other or reacting to one another. Random different poses on opposite sides is where I've seen things tip into looking accidental. If yours glance toward each other across the buttons, that might be the sweet spot.

The hanging possum sold me on the whole design, that's the kind of thing people remember. I did two raccoons on a denim jacket last fall, one pawing at a trash can lid and one just sitting there looking guilty, and my niece refuses to let me give the jacket away now. Two poses just give them a little story. On the eyes, I'd pin it flat and check tomorrow like the fox poster said, but if it still looks off I'd unpick just that one eye rather than both, since redoing a single small element is way less risky than fiddling with the whole face.

Possums hanging by the tail are peak possum behavior, you nailed it. I did a moth on each pocket of a denim vest once, one open-winged and one closed, and nobody's ever called it sloppy. If anything the odd one out gets compliments first.

For the drying thing, I've had wash-away residue make fabric look wonky way longer than expected, expecially on thicker knits. It can take a couple days before everythign settles, so don't rush the eye fix. And yeah, where'd the possum design come from? I've got a jacket that needs one now.