Increasing Header Button Size

I am revamping my website and I have a couple of ideas brainstormed but having a hard time applying it to the Enfold Theme.

I currently have a left side bar with my menu, but I am planning to move this to the top and creating a header. However, when I do, the buttons seem very small, and there’s a gray outline that I don’t really like.

If possible, I would also like to display a picture (could be a slider) but I cannot figure out which slider I should be using. I would like to display different pictures every time somebody refreshes the page. Is this possible?

A perfect example that I found online can be found here: http://woddrive.com/ (this website has large header buttons and a nice slider).