Next trick, set up your planting area. Where do you want to see this design from? Is it to be a secluded area behind the house, or a display at the front? You want to see your design from the right place, so maybe it's for a seating area, or back or front doorway?
Have you got an ugly shed to hide?
Then, you will need to sort out the bird bath as it is the centre of the picture.
In the picture above there's a SMALL silver leafed tree, probably hiding an ugly shed. There is then a background of silver leafed perennial plants, intermingled with tall white flowers. Stick with perennials, then the basic scheme will be there every year.
That will sort out your framework.
Before buying or growing anything, check what sort of soil you have. Is it acid or alkaline, clay, loam or sandy? Check shady areas and sunny spots. Prepare the soil, and find some nicely matured manure to dig in if you can.
That should keep you busy for a while
PS the one on the bottom right hand corner is Stachys byzantina aka lambs ears.