Paint and colours
In the house, you can use white or another pale paint to make rooms look bigger and brighter. Again, this can be translated into the garden.
Paint fences and walls white or bright colours to make the whole garden appear bright and big. This is especially effective in city or town gardens where light is sparse.
Warmer colours such as terracotta and primrose can be used to add Mediterranean character to a garden spot. In the home, a chimney breast or feature wall in these colours make great statements in rooms. This is something you can start doing in the garden too, by painting your shed, summerhouse or even large planters with these sort of colours.
The other effect these warmer colours have is to make items appear closer. To make items appear further away, colours such as pale greens, purples and blues will do the trick.