Is it possible to turn a picture taken with an iPhone into..

[Big Rig]

A high quality screen saver picture for my laptop?

Apologies for what is probably a very dumb question but I know nothing about photography. I have a picture of my dog on my phone that I would dearly love to be my screen saver. Can I do this?

[SHutchinson]

Yes. Email it to yourself.

[Tycho]

Assuming you backup your photos to iCloud then login to icloud.com in your browser and download it from there.

[Simpo Two]

Screensaver (ie moving) or wallpaper/background (static)?

[sgrimshaw]

Screensavers do not have to be moving, you can select "photos" and then choose a folder which contains the image(s) you want. One image in the folder is fine.

There is also another place to display images in addition to wallpaper and screensaver and that is the lock screen.

All of these settings are found in the Personalization section of Settings.