Dr Geep made a tut about Sketch Designer, explaining which setting does what. I don't think you can go any better with it, but maybe try to use some pre-defined presets ? Over at Animotions' Freestuff there's a nice pack of Sketch Designer presets. I had very little luck myself with that thing. I got one pic at my gallery as an experiment, but I guess it was a failure. Interesting, yes, but not as good as I hoped.

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Outdated gallery over at DeviantArt

Fics at FanFiction.net and Archive of Our Own (AO3)