I'm assuming that's you with the face blocked out. (Would smash all those girls). First, I suggest contrast. Dark pants-lighter colored shirt, or vice versa. Your current look is too dark and looks bland.
How can you casual it up? Easy. Lose the tie. Roll up the sleeves, and change to less formal shoes. You can also change belts (in fact you should) to go with the shoes. Something fun and more casual. Just store the accessories in your office and you're good to go.
Edit: sorry just read your post. I think you're doing pretty much the right things. Aside from bringing an entire change of clothes, shoes/accessories are the way to casual it up. Are you in a hot climate? Can you wear linen pants to work?
How can you casual it up? Easy. Lose the tie. Roll up the sleeves, and change to less formal shoes. You can also change belts (in fact you should) to go with the shoes. Something fun and more casual. Just store the accessories in your office and you're good to go.
Edit: sorry just read your post. I think you're doing pretty much the right things. Aside from bringing an entire change of clothes, shoes/accessories are the way to casual it up. Are you in a hot climate? Can you wear linen pants to work?