I've heard people I respect say that we should only sing the psalms, or the old hymns.
The Psalms themselves however tell us to sing new songs:
2 Praise the LORD with the harp; make music to him on the ten-stringed lyre.
3 Sing to him a new song; play skillfully, and shout for joy.
Psalm 33:2-3 NIV
The following song originally had a harp instead of the piano that's replaced it. I wrote it back in 2007 with a basic hip-hop feel to it. It's a contextualised urban worship song, following the biblical principle of making music to God with the harp, and singing a new song (Ps 33:2-3).