Using the seven colours of the rainbow as an example palette and the theme of a Mind Map here is a quick tip regarding colour placement
When adding images, the colour you use for each image has a dramatic effect on the overall appearance – I am using clip art here to demonstrate; view the colours only, rather than thinking what colour each object might normally be:
Colours rearranged, the images fall in similar areas yet this version is more interesting – the colours help bounce the eye around the Mind Map and also make it more pleasing to view as a whole:
The ideas above are not hard and fast rules and the differences are often subtle, yet worth considering when building your Mind Maps or any other artistic compositions