You probably want to look for pieces that don't have a gridded background (just all white). These pieces are not locked to a grid and can be freely moved around.
For example, there are 4m wooden posts that are gridded but there are is also the same post that is not gridded. The non gridded can be placed next to each other forming a short wall.
Look out for non-gridded pieces - there are lots of them and they can be used to good effect. You may also be able to use the art shapes to 'fill those gaps'
Hope this helps