As a newcomer in these parts I welcome you! ^^
So far these look good, the Diancie recolour being my favourite. The way the colours blend together is just right, so good job there.
I feel there is something a little off with you Blaziken and Fennekin trio however, and it looks to me as if the colours don't quite sit right. The execution of the colours is good apart from in the Blaziken piece. I think the blues used are a little too bold, and strain the eyes a little. With the Fennekin trio, I find the colours quite distorting, for want of a better word, because I don't think the turquoise complements the purple properly, as it is supposed to. I would suggest using a lighter colour, to prevent the colours from clashing.
tl;dr try and stick with one main, vibrant colour, and prevent the others from stealing the focus. Also, try not to use colours that are too dark. In the Blaziken piece, details of the Pokémon are lost because the detailing isn't clear. Those would be my recommendations to you!
But Diancie is good, try and use her for guidance with your next pieces!