depending on the orientation and time of day different parts of the yard will be more or less comfortable throughout the year and it's good to plan the outdoor spaces to suit specific activities and available space. describe your climate and draw a plan of the block showing direction of north, driveways, sheds, special views, big trees and the house with location of kitchen and all external doors and distances from outside walls to fences...a hand drawn sketch will be enough and include a description of anything you would like to include and who will be using the outdoor areas and we can make a site plan to help identify options to suit your family activities

I'd start with the basics . The fences , which seem to enclose 3 sides , let the place down . I'd go with 4 or 5 10 litre pails of fence stain , in charcoal/black -- I dislike Brown ( too 70's ) but I don't think it would suit anyway .

Then some colour , and 1 focal piece . I'm in NZ , so not sure plants to recommend , but maybe a palm ( or two or three of differing heights ) as your focal point , and some colourful semi-tropical plants . The existing garden along the fence probably stain the low wall in the same charcoal black , to tie in with the fence , but add a lot of light / white pebbles , shells and similar -- any coloured plants or flowers will be highlighted .

Then , depending on budget , build in a barbeque , with paving . off the covered area , and add a sail shade -- set up so it isn't over the barbeque area , and use a brighter colour canvas -- that yellow 'box' that is in the 3rd picture of yours stands out -- a sail in that colour , or mid orange or red , a reasonably vibrant green or blue , or even a neutral grey , will add colour but also distract the eye from the rectangular shape of your house .

From there -- do what you like / can afford . The sky is the limit -- playground , pool , spa , water feature , sculpture -- wherever your taste takes you .