Earth Giant: I will be honest, this was my favorite entry in that contest. She looks so beautiful and elegant. I'm almost positive you haven't watched Winx Club since it's about fairies and whatnot, but she reminds me of the character Flora, who is the Fairy of Nature. I like that she has a more earth-y skintone, and the background and flowers meld really well. I also like that you had the ingenuity to use a shuni head over the base; it works extremely well. I didn't even think to do that.
Water Giant: I wasn't as much a fan of this one as I was of your earth one, but I think that just comes down to personal taste. It's just so dark, but that's the concept you were going for, so there isn't really too much to say. Though, as you mentioned to me (which I think was right on the money), changing her outline from the light purple to something with a higher contrast could have helped her fit in more.
Franken Cutie: I don't even REMEMBER this contest, but I love the head you chose and the edits you did. The background also fits the "cute" aspect of the doll. I probably would have a chosen a more "fun, funky" text, but you might not have had them. dafont.com
is a great place to find interesting, free, downloadable fonts you can add in to GIMP. Also, the color of the text makes it blend a bit into the darkness of the background. The shadowed part doesn't always have to be black; here, I would have used white or a similar light color for the backlighting. And as Lovie has done, you can duplicate the font a couple of times so it sort of makes an "outline" that helps make it easier to read. Regardless, it's still a very cute, well executed doll.
Pirate: I am a HUGE fan of this one. I love the outfit you gave her, the frame you chose, the way she has a fir, and a map, and a sword, and is just so...pirate-y. I agree that shadows could have given it a slight extra edge, but it still looks awesome. I might not have used so pointy a flame, but it still works, and I like the lighting on the ground. You also glittered this thing masterfully, so kudos for that!
Purity Princess: This doll is excellent! I love how you used light blues and lilacs to make the white's brighter, and the grayscale works very well. How creative to have her home in the clouds! I'm quite fond of the doves you used as well. I admit, though, that I didn't even know she had a tattoo until you pointed it out. (side note, looks like you forgot credit on that one?)
Rogue Princess: First off, I'm going to need you to tell me more about this GIF scrubber extension; it will make my life a million times easier xD I really like how well the crimson stands out against the white forest and snowy background, with the only downside being that all of that white is very reminiscent of the purity doll. It's still stunning, though, and the gently falling snow is a really nice touch. I appreciate the fact that some of the grass goes above and in front of the hem of her dress; it really helps place her in the scene rather than leave her as a pasted on segment. Only CC is that the text is a bit hard to read; maybe a different font or a larger size could have helped? It still looks awesome, though, and the frame fits wonderfully. Kudos!