Consider where the windows and doors are to help determine where a feature could be placed, but I'd suggest straight out from the step towards the end of the lawn (especially if there are glass doors behind this step). Perhaps a feature tree with under planting or a secondary seating area under a pergola. It is quite a distance from the deck/house so would need to be relatively large.
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You could do something quite cost effective (just a simple chip area, bench seat and pergola with climbers) or more elaborate like a deck. Here are some ideas :)