This is not possible in OOTB. if you want to display attached image, need to customize Edit and Display item forms with the help jquery you can display the image.
The other way around is you can user image column instead attachment, the image column is OOTB field. If you want to try this, below are the steps.
1. Create a site column and the type is "Image with formatting and constraints for publishing"
2. Add this column in you list content type(Enable allow content type then add this column in to list content type)
3. Now upload the image then view it in Edit and in Display forms.
Note: The uploaded images resides on a SharePoint library(that is selected while uploading the image)
Hope this will help you.