Is it the shady side or the sunny side? Is the ground earth or paved? Most climbing plants, like clematis, honeysuckle, variegated ivy, roses, should do it. Or you could be contemporary and plant bamboos (the non-spreading ones) along the side, with touches of colour between them, like allium Purple Sensation. But any of those will hide the shed to some extent.
I was lucky enough to inherit a shed and then a really mature Clemantis Montana that has been growing all over it.. I would go for this plant to cover anything. It does grow like mad but is very attractive, beautiful flowers in early spring. it requires very little attention.
The only disadvantage is that it does go to stick in the winter
John Mcleod, would that be Virginia Creeper? I have 2 sorts on my house. The one with divided leaves is very very vigourous and grows where I don't want it. The other, more palmate leaved one is neater and attractive, but it still needs at least a metre pruned off every year to keep it off the roof.
you cant beat star jasmine, its evergreen and smells wonderful in the summer and the leaves turn a lovely red in winter. Slow to get going, but be patient, you will be rewarded
Clematis Armandii is hardy, evergreen, and has cream, perfumed flowers late winter and spring - quite exotic, I think, and you could grow another clematis to grow alongside or up it. Passion flower or the evergreen Jasmine might be good, too - the latter has small but lovely smelly flowers for much of the summer
If you don't want to hide the shed, Frozz, how about rosemary? Evergreen, flowering, and edible!
Or winter flowering jasmine for glorious bright yellow flowers in the cold months. Also evergreen. Does need to be kept under control by judicious pruning.