What are you using the Hero Images for? Typically I would have a corresponding Landing Page built and track the number of people going to the landing page to understand how well the promotion, offer etc was working and then you can track conversions if you were giving a free trial, or downloading a coupon, etc.
There are other ways to approach this depending on the application, but that is where I would start.
what are best practices for design these types of images?
Not to speak directly to the design question (I find hero images boring, or so says my conscious mind) but if you're also changing the text that's used on the image it's broader than "what's a cool image" -- you're pairing the image with a tagline, so it's a question of how catchy the text is and how well it's subtly supported by the image content.
But that's neither here nor there...
Is it a best practice to track these types of clicks?
It's a best practice to track all clicks, right? But as Chris notes, the question for internal links, where you control all the available metadata about the click, is whether to do source-based or destination-based tracking, and to not be confused by doing both.
- you can catch the clicked URL on the source page and pair it with the current document URL to see their click path; or
- you can catch the pageview on the destination page and pair it with the referrer URL and/or internal UTM params to see the exact same info
Like Chris, I would err on the side of destination-based pageview tracking, with the links being source-encoded (with UTM or equivalent info in the query string). But you never know what C-level people will demand in reports. If they want to see "Clicks" then you've gotta do clicks.