Have a look through Behance and Coroflot for examples. I don’t think there is anything wrong with showing ‘raw’ work like basic mock ups and sketches, even if it doesn’t feel presentable. Not everything has to be a polished render, just make sure that it helps tell your story and is understandable.
You have a lot of great prototyping work where you’ve clearly been thinking about how the product was going to work, so I know that you’ve come up with a number of ideas, but in the folio you’ve condensed all of that work into a single little thumbnail on a page. I think it would benefit from showing more of the hard work than the finished product.
For example, on the spray gun, I would condense pages 14 and 15 together, drop page 19 and 20 altogether and use the painter image as the money shot backdrop for the project intro on page 13. Then use the 3 pages that you’ve saved to really show all of the work you’ve done with larger and more dynamic images.
As Yo has said, this is also just my opinion and my particular point of view. I hope that it is helpful.