For your first times, not bad at all!
Some suggestions on the second signature; blend the render a lot more... use the soft brush tool and erase around the hair at the least, a bit of blurring would do some good too. Don't overlap the all the bubbles, move the last two out farther so that maybe half of the biggest one is off the edge of the signature, or you could just space them all out, but the overlapping makes it look too uniform.
Last suggestion, use a fractal brush with more flow. Some brushes are better executed in different ways and this isn't the best way to use that one. The crisscrossing pattern makes the eyes wonder way too much.... Also, give it a layer effect... maybe overlay or linear dodge....
EDIT: One last thing, the red in the left hand side doesn't look good. A simple fix is highlight it with the elliptical selection tool (select a circle a little bigger then the red spot so there's room after the next step), go to Selection menu>Feather>20px. Now, make that black and white then go to (without de-selecting) image>adjustments>color balance I believe and tweak it to fit the rest of the color scheme.