Bye-Bye Bow Tie
Stylish groomsman are seen more in tuxedos with long (not bow) ties, with vests instead of cummerbunds, non-pleated shirts, and three-button jackets. All of which is a more modern option.
Beyond the Tux
If you're having a casual affair, feel free to ditch the tuxes. Instead, dress the guys in blazers, and match something in their outfits (for instance: a pocket square, a tie, a belt, their socks!) with the overall colour scheme. Or maybe order extra fabric from the bridesmaid dresses to make matching ties for the groomsmen -- this is a great way to tie the party together.
Perhaps give your groomsmen a unique, personalized gift that will add to their wedding day style and that they'll also be able to use again and again. Cufflinks, pocket squares, socks or ties with their initials monogrammed on it, make a great gift.
Vary the Boutonnieres
Instead of going the traditional route and having all the groomsmen having identical boutonnieres, which is total acceptable. Perhaps the every single groomsman boutonniere is different but match them with the bouquet of the bridesmaid he escorts down the aisle. Decide what each pairing will be by using different colours of the same flower, or all different flowers in the same colour.
Mismatched Groomsmen Tuxes
Similar to the mismatched bridesmaid dress trend, the groom and his groomsmen can totally get in on the mix and match craze too. Remember the main man gets to set himself apart with a unique suit or tux, while the groomsmen wear complementary looks that are each accessorized a bit differently. Give your groomsmen a specific colour scheme to follow.