I'm afraid I'm not familiar enough with magic sigils (and alchemy, for that matter) to figure out what needs to be adjusted :). Could you give examples of sigils that are too scientific and sigils that are mystical enough?
Basically something that looks more like it was written or drawn by hand and less technical. As far as an idea for what they may look like, take a look at the Nordic runes for inspiration here.
I also wonder if it's possible to set it so we could alter the lines and such to more of what may be needed.
I think Rune Generator produces runes which look somewhat similar to norse runes. I did some tests with the hand-drawn style, but didn't publish them as something interactive.