Instead of working on a new technique or song, just play. Have fun and just enjoy the fact that you get to play bass.
You might want to try writing a song or riff. This is a creative way to come up with cool new riffs or song ideas to bring to your band.
Play a song, but try to create a different bass line. This can be hard for some types of music but for most rock songs you should be able to play along with the song.
Just do something fun and remember why you love to play bass.