Here are some resources I used for creating these free Keynote templates.
POWERPOINT
Do you need PPT files (for Windows users) instead of Apple keynote (Mac users)? Try best powerpoint templates website – many free powerpoint files there.
IMAGES
Most of the images used in free Keynote templates are from these websites:
• Pixabay (I am an author there by the way)
• Freeimages (earlier known as sxc.hu)
VECTOR IMAGES
Recently I found FreePik, which looks very promising. Use vector elements from FreePik website in your designs to make your presentations extra special.
ICONS
In latest designs, I use free icons from SmashingMagazine. Some other great resources for beautiful and free icons, which you could import into your Keynote template, are IconArchive and IconFinder.
COLOR THEME
And finally, I suggest a consistent color theme in any keynote presentation that you create. I used this great free color theme generator.