Even so, the version of the MiniPlayer added with iTunes 11 includes the Up Next button. And if you want to listen to something specific, you can search your entire music collection via a search box that appears in the MiniPlayer when you mouse over the album cover art and click the magnifying glass. Click the MiniPlayer button to shrink iTunes.
In MiniPlayer itself, you can choose to show enlarged artwork (album cover) or go with a smaller thumbnail. And if you want to keep MiniPlayer in the foreground on your desktop, visit iTunes Preferences, click Advanced, and select Keep MiniPlayer on Top of All Other Windows.
Go in the opposite direction and make iTunes take over most if not the entire screen again by clicking the Mini Player button a second time.