As the appearance of the garden has a modernist style with the straight lines and concrete furniture how about a Mondrian influence and add a bold strip of blue? It is a pond and with the right shade it could look really relaxed and contemporary. My daughter's suggestion is a chalky lilac!

Thanks for all the great ideas everyone and sorry I didn't explain the polycarbonate a bit better :) This is along the lines of what we'll be using... http://www.psp.co.nz/building-brands/corrugated-sheeting/suntuf-polycarbonate The area is an absolute sun trap and we're hoping to use it as an extension to our living space, especially on rainy days! I've just sent my husband out to get a few pots of different stains for is to try - darkest brown (cedar) and a lighter brown (rustic oak) both by Cabots + the black we already have. Hopefully we can decide between one of those! I probably should have mentioned we will have black aluminium pool fencing running along the top of the second retaining wall - so the real question is do we keep everything black (pool fencing, horizontal fence, retaining walls and pergola) or do we go with a dark (or even light) brown for the pergola and retaining walls.... We just keep going around in circles at the moment. Decisions, decisions! Thanks again :)

Textured linen or with a subtle print wont date. Feature walls make a room smaller as they jump out ar you. Wouldnt recommend. Get some interesting art or craft. Pick up colour with accesories

The photo gives a bit of an idea , but an inside shot would really be needed , plus an idea of your favourite things . Probably the two best guesses would be art on the walls , and/or plants . Plants would only work if it 2 metres or more deep , but boy could you have fun , with different coloured leaves , textures , heights , leafy plants , cactuses , all sorts . A marble statue or a rock water feature depending on style and taste . Art is more personal -- family photos may be important to you , or you may like WW2 planes , or large colourful abstracts may suit your tastes and draw looks . Other things like a wallpapered feature wall , even timber may work , but you need to suss out what suits YOU -- unless you want a home and garden magazine clone .