A cover for a book to be sold through ebook and print format. The spine for print version (CreateSpace) would be .493 inches.
The book is about a CIA project (in the 1950s and 1960s) involving chemicals...etc. used to brainwash people into doing the CIA's bidding. The main characters are a sexy female agent (with red hair) and a male, as the protaganist, and one main antagonist.
The most important point about the cover is to make sure the title sticks out with contrast and is visible at the standard Amazon thumbnail size, 114 X 160x pixels. My book formatter said the cover should be 2400 times 1600 pixels.
A slug line "Murder, Drugs and Spies" could be useful as well as a sketch of the female agent with red hair (maybe holding a gun??), as long as it doesn't take away from seeing the title. I have no pre-conceived notions, however, so you have some liberty.