How to ‘design’ this area…

[MoreChocPls]

Got a garden area which is 10ft x 20ft, partial shade, currently just a bed of weeds. Was thinking about doing a cross with grass and having a bench at one point and leaving the rest as just grass then filling in each corner square with some plants and a rockery at one end. Was thinking of some raised flower beds for annuals and vegetables, and fillings gaps with bushes/shrubs etc. Putting lavender down one-side. There is a path/patio on 3 sides and fence the other. What do you think?

With a small garden I would eliminate a lawn altogether. An arch lends interest without making the garden look smaller.

Two ideas -

I think that the shape of your design echoes the shape of the plot too much. I understand that squareness is easy to construct but it looks too basic.
I would introduce some curves and softness. Or change the angle: you currently have a "St George's cross" but you could make it a "St Andrew's cross" instead. You would still have your lawn-cross but the arms (now the hypotenuse) will be longer; it will make the whole garden look bigger. Google "garden design on the diagonal".
Where will you store the lawn maintenance equipment, btw?

You want a bit of mystery in the design; you don't want to be able to see the whole garden in the blink of an eye. PP's arch feature is a good example of this, where the arch and the tubs make it difficult to see exactly what is going on. It gives a sense of intrigue.