WordNet (r) 3.0 (2006):

envisioning
    n 1: visual imagery [syn: picturing, envisioning]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "envisioning":
   Vorstellung, concept, conception, conceptualization, eidetic image,
   envisaging, image, imagery, imagery study, imaging, imagism,
   imagistic poetry, lifelike image, mental image, mental picture,
   mental representation, objectification, picture, picturing,
   poetic imagery, vision, visual image, visualization,
   word-painting