Hello and welcome to Apple Support Communities, gtowle!
I understand you've noticed that the preview for when you take screenshots no longer shows up and you're stuck with an outline of where the screenshot area was. I'd be happy to provide information that may help you out.
First, check your settings for screenshots: How to take a screenshot on your Mac
"Change the settings
Click Options in the onscreen controls to change these settings:
- Save to: Choose where your screenshots are automatically saved, such as Desktop, Documents, or Clipboard.
- Timer: Choose when to take the screenshot: immediately, 5 seconds, or 10 seconds after you click to capture.
- Show Floating Thumbnail: Choose whether to show the thumbnail.
- Remember Last Selection: Choose whether to default to the selections you made the last time you used this tool.
- Show Mouse Pointer: Choose whether to show the mouse pointer in your screenshot."
Test if the outline continues to appear after modifying these settings.
If the issue continues, test to see if it also happens within safe mode: Use safe mode to isolate issues with your Mac
I hope this information helps you resolve this issue.
Have a great weekend!