Are you looking for feedback? From your description it sounds like you're done, but I see something that you could definitely improve on if you want to spend another 20mins getting it done:
- You can really tell you're using the vectored strokes (PS Styles), especially on the Space Invader beast. The stroke definitely doesn't look clean, because the source image was probably scaled up from a low-res image and not thoroughly cleaned-up. Or you've got the stroke width too high, where you're losing the sharp corners of the details.
There are two things I'd do to make this look cleaner:
1. Since you're only dealing with 2 colours, it would be beneficial for you to trace this guy with the pen tool (making vector shapes), convert all the shapes to a Smart Object, then applying the stroke to the Smart Object itself. Make sure that the white parts of the beast is filled in of course, so you don't get the stroke applied to the inside of those areas. Doing this you'll have a cleaner source for the vector stroke to contour.
2. After applying the stroke to the Smart Object, create an empty layer, merge it together with the Smart Object (effectively rasterizing the SO -- you can make a copy of the original SO Layer and hide it for future edits), then go around the stroked lines and with your eraser/marquee selection to sharpen up the edges.
This whole process shouldn't take longer than 20 minutes, and it would make that image look 100x nicer.