My guess is this was designed like this for one of three reasons:
Option A: Lebron is the face of the franchise; AV has been around the longest; Love is a key free agent; or
Option B: AV and Love aren't going to play in the Finals, but the Cavs want to reinforce that they're still a big part of the team; or
Option C: The Cavs are trying to be "inclusive" and market to blacks, whites, and Latinos by including a player of each heritage
For whatever it's worth, Irving, Shump, Delladoeva, and J.R. Smith are the Cavs' twitter background image