Camera should fit the microscope adapter and have the resolution you need to clearly distinguish centromeres and banding of the chromosomes.  I don't think you'll need much special although if you're using fluorescence you may need the ability to use certain filters.  You'll want to be able to control exposure manually and avoid major color shifts due to non-reciprocity.

I know it is a bit too late, but maybe for the future....

http://www.lucia.cz/en/front-page/lucia-karyo

People there are very nice and friendly and willing to help and advice (at least I have good experience with them)

Thanks so much for your answers, have been really helpful :3