I can only find "I will leave the rest to you" but not "The rest is for your imagination".
Let's say I'm introducing a software which provides a wide range of separate functions. Those functions can work alone, or can be combined to solve a user's problem. The user can freely combine the functions the way they want. After the initial introduction, as the conclusion, I want to say:
The software provides multiple basic functions, the rest is up to you [the user] to combine them, let your imagination fly.
I'm trying to paraphrase the part 'Let your imagination fly' to 'The rest is for your imagination', however I'm not sure if it's right and/or natural.
Best Answer
the sky's the limit (idiom)
It also ties in with your slogan Let your imagination fly.