Mind- I paint more than just at those practice spots. Those spots are just where I try and put out quality. I'm still fairly new to the city where I'm living, so I only really know like 3 spots that are good for daytime piecing. Everything else I do I'm more paranoid about, so I paint at night and spend less time on. I've been writing for about a year, so I still have lots to learn.
I've been painting trucks lately, but just straights and throws. I don't flick them because I don't bring a camera. Plus I paint at the depot or whatever, and they are all parked really close together so you couldn't get a good photo anyway.
ECO - Looks pretty good, but I think you have some of the same problems I do. Some of your lines look pretty unsteady, and vary a lot in thickness, particularly your O. See how on the purple one your outline goes from thick to thin in some places? You want it to be perfect and uniform. A lot of it is just developing can control over time, but there are some things you can do to make it look cleaner.
Once you have your fill done, and drop shadow outlined, do your halo, THEN do your outline. Try and use consistent fluid long strokes. If you screw up a part and wobble, hit the whole line again. They go back and clean everything up. Fix any slip ups that drift into the fill, fix anything that goes too far into your halo. If you screw that up at all (fill drifts too far into outline) hit the outline again. Hopefully once you do that, it will look nice and uniform. Also, cutting back like that is how some people get those paper thin almost graphic looking outlines sometimes.
Also, some of your letters look a little wonky to me. Your E seems to get thicker around the bends than it is at the ends, and none of your other letters really do that. I don't know if that's intentional or the proportions are just a little off. It could just be me though.
Finally, the C on the purple number is missing some drop shadow.