Glad to hear you're liking Sketchbook Pro, it's definitely the best piece of software I've found for sketching! Keep it up!
The Nike Arc Angels shoe by Guercy Eugene is a great reference to use both for presentation but also process. The biggest disconnect I see between Guercy's project and what you've presented so far is you still haven't presented a problem statement.
What are you trying to accomplish with this that hasn't already been done? Just making a boot that has the national colors of a team and some curves isn't really going to be much to talk about during an interview.
Any big boot launch will have a technology, and in the best cases that technology is based on a key insight (athletes want to cut faster, athletes want better ball feel, athletes want a more flexible platform, etc.). Right now this just feels like a color and graphic exploration, so I'd challenge you to push further.
SeanKelly wrote: Thankfully, Photoshop has a liquify tool to alter the shapes to look more realistic. \
I wouldn't get in the habit of doing this, in the long run it's better to get familiar with the proportions even if it means sketching over templates. Some of these are decent, others are really far off to the point that it's distracting to the design.