Lego Rocketeer from high
This is by far the largest mosaic i've made. If I used 1x1 bricks only, it would use 30,672 of them.
It stands 45 inches (3.75 feet) by 66 inches (5.5 feet).
It took somewhere in the neighborhood of 70 hours to complete, and required about $400 worth of Lego in addition to the pieces I had on hand.
Likely if you had to buy all the pieces, you'd be in $1000 range.