Others here are better players than I am... I'll let guys like Robert throw out a few pointers as far as technique goes.
Playing to backing tracks is a great way to firm up timing, and to try new ideas out about soloing. Yes, you should be standing, and have your guitar set to a comfortable height if that's how you play with the band. It's easy, though, to learn a few stock phrases and use them in different keys. That'll stagnate your playing quicker than anything.
The easiest thing to do for me when I feel like I'm in a rut musically is to listen to another genre of music, find something that interests me (chord choice / progression or lead phrase), and learn it. Incorporate that into your playing. Doing that does a few things:
1. It gets you out of your musical "comfort zone."
2. You have to listen to new and different artists.
3. You can then add variety to your playing.
Also, are you writing any original tunes? Think about the music in your head, and try to make it come out the speaker. It ain't easy, but its a fun challenge.
Finally, DON'T LIMIT YOURSELF! Stay open to new sounds and try to replicate them on the guitar. You might stumble into a cool technique or two that way as well.