Depends on what your skill set is and what you need. If you got the necessary photoshop skills, go cook yourself one up. No biggie.
If you want to attract from the cover itself, however, then by all means, go for it. Find those that do good landscaping art with high contrast in eye-catching colors (royal purple, magenta, green/yellow, something big and magnificent and holy-shit-why-isn't-this-in-the-Louvre). As long as it catches the ye, it's a fair chance that it'd do too with readers.