For the first question:
1. A custom Boolean attribute can be created
2. A custom logic can be induced to set this attribute to true, for one instance per project or so
3. A default filter can be published for the list view, that only displays instances that have this attribute set to true
For the second question:
Here again, a Boolean attribute can be displayed as an image. But you would have to choose from the list of 96 OOTB supplied image representations. The choices can be seen in a Boolean attribute definition page.
I doubt if it is possible to display an image read through an attachment field.