They were likely rejected for being just recolours of other sprites. Custom sprites are an opportunity for artists to not only be creative but have a go at rendering characters in the artist's own style. The recolours are great, but the effort is minimal (i.e. "low quality") compared to making your own sprites from scratch, because the base sprites are already done for you, and all you did was change the colours, in effect. If artists do use base sprites that are already official, they often make their own shading style to compliment it, which can take quite a lot of effort.
With Ness you might be able to pass with that one if you edit the shirt at least, but I could not say for sure. I'm not a reviewer of custom sprites, so I can't say for sure what the absolute guidelines are.
Anyway, this is the general gist of why you might have had them rejected.
With Ness you might be able to pass with that one if you edit the shirt at least, but I could not say for sure. I'm not a reviewer of custom sprites, so I can't say for sure what the absolute guidelines are.
Anyway, this is the general gist of why you might have had them rejected.