Great work, espicially considering your age and experience. Couple comments, the technique you guys each use is very pro (I can only wish I had your talent) so there's not a lot I can say on that, but maybe we can give you some tips on the thought process.
Yo's comments on the Nautilus point at something that might help both of you, which is coming up with an overall art direction for the body of work- a vision of the world that these characters and stories take place in. Not saying it isn't there already, it could very well be, but I think it might be good to pick up the book/story and come up with factors that can be used as metrics to steer your aesthetic styling; is there a mood/emotion/feel, a technical element, a geographic or historical influence? Put those things down in writing, and use them as a starting point and a tool for guiding your creation process.
You can come up with this kind of rationale for the overall aesthetic, and then break it down into sub groups of character groups, environments, to individual elements. I'm sure you've seen some of the making of bits that WETA did for LOTR- they came up with a culture for each race, and used it to inform everything surrounding them-architecture, clothing, props.
Anyways, I think putting some thought in before you put the pencils down can give your work a really compelling story, and show you have a thought process behind the pretty work.
A couple comments-
Danny- Not really familiar with the speedracer world apart from some old memories- I found a recap of your episode on tv.com,might be helpful to put that up as a starting point. Looking at your sketches so far, there's a pretty big style jump from the old speed racer character to the new one. Old is a collared jacket wearing helmeted guy, the new doesn't look particularly human or like he has much to do with racing in general. Maybe let us know why he's changed like so? Also since you're posting on an I.D. forum- what does that armor do that helps with racing? I see nutrients for racing, but I wouldn't want to sit in a car long enough to need food and water in a piece of hardware like that. There's some interesting exo-armor stuff in racing, like neck braces and the armor motocross guys wear, maybe looking at that stuff can help bridge storm-trooper to formula driver.
Character studies are great, really nice explorations that suggest a period of time and style- but like Yo said maybe its a good idea to step back and consider the world the story is taking place in. Is there something new that you can bring to the story other than a restyling of the old? Referencing parts of the old is good, but why stop with simply restyling? Like how you looked at Nemo and some of his surrounding objects. The diving suit feels a little more like halo than deep sea explorer.
Great stuff, and I look forward to seeing more!