Two different .mp3 file icons on Mac ?

u have downloaded some songs all 4 in .mp3 extension and all playable in itunes although 2 have album artwork/black box as icon (which allow you to click the icon to play without opening itunes) and the other two have a classic white paper with mp3 logo in them which dont allow preview.as their both the same file type converting the mp3 to mp3 wouldnt do anything,btw this is because the 2 with artwork play on my blackberry wereas the two without dont ?