The sprites are fine, it's just the palettes. I just think some the original palettes don't work. Like the 'King of Dragons' sprites have too much contrast and are very bright. While D&D sprites are more faded less contrast. King of Dragons sprites IMO are too colourful to begin with, and the backgrounds were too faded. Very strong greens and yellows in those sprites, but that's more personal taste.
I just mean doing something like this.
Original
Darker more faded style.
less colour, increased contrast
Like here, this dwarf is a main offender. See how he is against the background?
See this guy too, he is too bright and colours look too faded.
Background and chars, too similar in brightness and contrast. In every game you will ever play, background will be darker or more faded than chars.
this background is very out of place, it at least needs more contrast. But this painted background style should probably be avoided altogether.
Looking at some of your custom made sprites, they have nice darker palettes. If you simply edit other chars to match your own style/tastes it will look fantastic.
Anyhow I'm not nitpicking, just mean decide on a certain look and edit the rest to suit. Like if you want it to look like original D&D and KOD games then edit other chars to match them.
Personally I'd try make them look more like this guy. The helmet dude (warduke?) has nice dark palette but not too faded either. but sprite behind him, colours are very bold and a bit bright. The dragon is a litte faded and could use little more saturation.
But overall this screen looks better.