Do whatever it takes to boost that GMAT score. Sign up for a GMAT class/course, hire a private tutor, etc.
If you can score in the mid-600s, then you may want to look at part-time programs like Langone (NYU), UCLA FEMBA, Haas or USC. Since you're staying more or less within the same industry (but transitioning into a different job function), you're right that part-time will probably make more sense.
It really comes down to your GMAT (assuming you can put together strong written applications and you interview well). From what you wrote, you have a profile that adcoms like - business-oriented but in a creative/artistic industry.
p.s. I was debating between applying for traditional colleges or art schools back in high school - my art teacher went to Parsons actually and was trying to encourage me to apply there. Sometimes I wonder what my life would've been like had I took the art school route...
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