Well done! I bet the neighbours are jealous and all your hard work has paid off. he lawn has obviously enjoyed the wet conditions we had this summer; looks great.
Is the land behind you likely to be built on? If so, I'd think of your future privacy/security - climbers like honeysuckle or jasmine or some hedging - berberis or pyracantha all good for wildlife along the back fence.
I was going to say a small tree in the farthest corner from the house but I see you have a tree already - what is it?
A small pond would be lovely with a beach (shallow sloped entrance for wildlife to get in and out ) would be something to aim for but even the smallest container can bring lots of wildlife
Do you feed the birds ? A lovely bird pole in the middle of the lawn where predators ( like your sleepy cat) would not be able to lie in wait - it would be a good time to start as the weather starts to cool down and you can sit and watch - brings me and my cat, hours of pleasure.