Okay, this is a lot of skin of yours so I will say only once in these skin. I am not sure should I believe those was around 2006-2007, most of these are fliter slap on it but i imagine 15 years ago you weren't artsy backthen.

• Priestess of the Demon: Barely noticeable with the stone texture on the cat and the only demon part is the face. Stone cat if executed right would have been a good skin.
• The Grim: Recoloring Acolyte with an outer edge red doesn't scream Grim to me. I think it's fine to leave the face black out but you could left mouthcloth blacken too. Doesn't really affect much the team color since you already have a clothing do it for you.
• The Vuurak: I can't comment this much, I'm sorry. Mostly Recolored.
• Redbeard Mountain King: Alright, I can give you prop for making the Avatar form but this is recolored and maybe a bit of effort put on Avatar Form would be nice.
• Flame Style Crypt Fiend: The only redeemable skin you made during that time, I know this is also recolored but it's actually a good recolor. If this Crypt Fiend got more effort on free-hand, you can get this one approved.
• Alliance Archimonde: Putting Alliance crest doesn't help this poorly filter skin. I have no idea what with the green stuff on the cape.
• Night Elf Jaina: Concept wise is pretty good but it could need more free-hand on it.

That's my review or at least some comment on your flashback texture brought here.

That mount is so ugly.

With all due respect, I have but a few things to point out for this skin.
1.) The sabre mount looks like a stone statue.
2.) Priestess of "what Demon?" The name should be changed so it at least says "Demon Priestess."
3.) This looks like a Blood Elf with a void, empty space with two red glowing eyes.

I agree with Shido that skins/textures like the Priestess of the Demon deserve some attention to detail. I've had an Art Professor who taught me something special about color. If memory serves, you can't just take a color and paint it on there; you must also give it lighting and shading. You must put a light source somewhere near the object, so you tint the side that faces the sun, and shade the side furthest away. When it comes to armor, the higher points often lose their paint, whereas the lower parts of the armor often retain those colors, and even then those elements have shades and tints to them.
I highly suggest that you look at this reference sheet, which talks about how to texture things nicely. Please note, however, that you can't rush art, as Woody's doctor from Toy Story 2 diligently puts it. Please also note that there are a few dead links (wc3c.net is offline for several months now.)

Don't discourage yourself when you try and improve on these skins, because we believe you can do it!

And the face?

This looks awesome! The face is the best part.

Approved as Useful / Simple. Thanks for providing an ingame screenshot. Looks interesting ingame.