Currently only out of box attributes appear as options in insight designer, that is current product functionality.  However, my organization for example needs to create financial reports based on a custom field we created called "Primary Region". That way we can encompass both cities and states into our reports to account for how different markets perform, not simply individual cities/states. More specifically, two of our markets are DFW and Houston because Texas is such a large state, but another market of ours is simply Arkansas - no more specific metropolises. 

This would help all organizations in that they can further customize their reports to meet their budgeting and development needs, knowing that every organization has its own priorities and unique needs for information to analyze.

We therefore should have the option to choose custom fields assigned to constituents and use those as a "row" or "column" option under Constituents under attributes for data.