Montana will get too big for a small shed. You'll need to provide a support such as netting, trellis or wires to support a climber as they can't cling to a plastic shed but you could then go for an evergreen variegated ivy which will give year round interest and flower eventually when it's mature enough - important food for insects and birds at a difficult time of year.
There are evergreen clems too which will look better than montana in winter - cirhhosa and armandii varieties are good. There's also honeysuckle to consider - Lonicera × brownii 'Dropmore Scarlet' is semi evergreen. Lonicera sempervirens is evergreen. Both will tolerate partial shade so, as long as your north facing shed isn't in too dark a corner, might be worth trying. They are good hosts for beneficial insects and provide nectar for butterflies.