I think that "the pictorial views of the mind" (phantastikai epibolai tes dianoias) is just a description of the the "visual stereotypes" (prolepseis), and thus they are used interchangeably.
I agree with the direction of this and given that it appears from Diogenes Laertius that it was not Epicurus himself who elevated the status of this to the level of a criteria, i approach the subject with caution.