Realia implements special content type for storing agents called Agent. This content type provides basic fields for agents as name bio email photo etc. We recommend to fill all this field to provide as much information for your potential clients as possible. In demo content we are using special handmade images. If you want same images but with different photos open the packed PSD files and directly change the photo in the design. After that copy the layer and use our new handmade image in your theme. It is recommended use high quality images for good display effect on retina displays.
Agent's fields are used in the Views so if you didn't fill some content the blocks or pages should be broken. If you decided to not use particular fields you have to edit views and remove fields from display. It's same when you add new fields. Regarding the agents page we are using views but all fields are hidden from display except the last field where we are rewriting the output of all fields to provide better styling. This is not good way but this functionality is coming from Views and there is any other way how to style these things.