Used to express understanding of a concept, not a visual image. After the long briefing, everyone said they got the picture.
Pro Tip 2/3
Informal Usage
Common in casual conversation, less appropriate in formal settings. When John explained the game rules, I said 'I get the picture' and we started playing.
Pro Tip 3/3
Slight Impatience
Can imply you want someone to stop explaining because you understand. Okay, I get the picture, you don't have to keep going on about it.