I'm not an expert in Salesforce by any means, but when I was asked to help improve the usability of some of custom components I decided why not.
Using the amazing Salesforce Lightning Design System as a guide I was able to use their sketch library to create high fidelity mockups.
On other components a UI and layout update were all that were needed, so in this case I would edit the HTML and CSS in Salesforce (locally of course), and then go through the process of getting my updates approved.
