There unfortunately is nothing you can do to that engine bay for free that is going to make a meaningful difference. But with even a few bucks and some elbow grease you can do some painting that could really spruce up some stuff in there.
When it gets warmer outside I plan on pulling the upper intake and the valve covers..
Painting the upper intake bright silver along with the Throttle body and the valve covers Blue to match the car. Also planning on deleting my A/C since I never use it, I've had the car for almost 2 year's now, and I've only used a/c like.. 3 times? Two of the times was when I had to drive me mum to the doctor, and one was on a 105F day lol