Make Finder desktop icon sizes huge
The Mac OS X desktop is attractive, highly functional, and very customizable, but by default the maximum icon size is 128×128, which is pretty large but if you have a huge monitor or you’re visually impaired you may want larger icons. This is where the command line comes in, where you can force the Mac OS X desktop to display icons as large as 512×512 pixels! Launch the Terminal and type the following commands:
defaults write com.apple.finder DesktopViewOptions -dict IconSize -integer 256
You can set 256 to whatever number you want, as high as 512, just be aware that it can get a little ridiculous, and 512×512 pixel icons will take up the vast majority of your screen.
Next, kill the Finder to relaunch it and see the changes
Reverting the changes is a matter of setting the integer variable to a smaller number.