Back in the 70s, Corgi Books reprinted the Bantam Star Trek episode adaptations with more uniform covers.
The US versions tended to feature variable pieces of SF art - usually variations on the USS Enterprise against a psychedelic space-scape.
The UK ones were simpler but more iconic - a giant number with standard elements peppered around it.
In keeping with my recent posts, here's a Doctor Who take on those designs.
I've also done a variant version of the original Star Trek novel 'Spock Must Die'.