~~ ja nai. = It is not ~~.
~~ ja nai ka. = Isn't it ~~?
ii = 'OK', or 'good'
So,
ii ja nai ka = 'Isn't it OK?' or 'Isn't it good?' (= 'looks good' or 'sounds good')
and,
'nee' is very rough way of saying 'nai'.
So, 'ii ja nee ka' is more rough than 'ii ja nai ka'.