Quote: "The licence for the artwork I have used is here http://creativecommons.org/licenses/by/3.0/, so as I understand it I can use it for commercial work as long as I credit the artist.
However, it remains to be seen whether or not this game reaches the point that commercial release becomes a consideration. "
You missed my Point

Using spicy pixel artwork or free stuff from other sites is almost the same as using mario or sonic art.
Alot of games already use them and most users have already seen the tiles and sprites.
I Think this guys art is great and reminds me of my atari and amiga Days.
I even considered to use this art as placeholders on some of my earlier Projects like my platformer for the intel appup competition.
Android 2.3 , ZTE Skate , 480x800 , 800 mhz , Samsung Galaxy Y , 240x320 , 832 mhz , Sony ericson arc 480x854 , 1 ghz
Android 4.0 , Dmtech 3g 9738B , 1024x768 , 9.7 inches , 1.2 ghz