According to MDC (https://developer.mozilla.org/en-US/docs/CSS/transform) here are the CSS transforms that morpheus is currently missing:

scaleX, scaleY, skewX, skewY, translateX, translateY, matrix, matrix3d, translate3d, translateZ, scale3d, scaleZ, rotate3d, rotateX, rotateY, rotateZ, perspective

In addition, the two-argument syntax for "scale" is missing: scale(0, 1)

Looking at the regexp in the source, it also looks like the second argument for skew and translate isn't optional. And it seems the regexp only allows a single space after "," but that can be easily fixed by changing it to use * rather than ?

Lastly, skew and rotate should use angles (https://developer.mozilla.org/en-US/docs/CSS/angle) and translate should use lengths (https://developer.mozilla.org/en-US/docs/CSS/length)

I'll be honest: the only one that I care about right now is scaleY, but I figured I'd include them all for completeness. I wouldn't blame you at all if you decided to not include the more esoteric stuff.