The phrase "picture mentally" can be expressed through various synonyms that point towards imagining or visualizing something in one's head. Some of these include envision, imagine, conceive, contemplate, envisage, fantasize and dream up. These synonyms help to express the act of creating a mental image or impression of something without actually seeing it. The concept is commonly used in fields such as literature, art, and design to help create vivid and realistic experiences through words or images. By utilizing a range of synonyms that accurately convey this idea, individuals can express themselves more effectively and bring their ideas to life in a compelling way.