By itself? No.
If you have a high density display in Photoshop CC you can set Preferences - Experimental Features - 200%, but you'll find that makes everything larger, possibly unacceptably so.
Have you experimented with Preferences - Interface and tried changing the UI font size?
Reminder: You have to close and restart Photoshop after making a change.
Perhaps if you have spare screen space you might want to make the Brush panel visible all the time. In that panel the currently selected brush appears with a little outline, and of course there's the stroke preview at the bottom.
Seriously, consider getting an additional monitor. It's a good way to work with a lot of panels displayed full-time.
Ah, sorry for misinterpreting your question.
There have been recent changes to shorten the dialogs in order to allow Photoshop to handle smaller displays with fewer vertical pixels (e.g., netbooks). We can assume this is just how they reorganized this panel in pursuit of that goal.
Ok, so there is no way to change this :/ ...thanks very much for you answer Noel!
have a nice day
Please tell me their is a solution to this. I have the same problem and I cannot see any of my adjustments to my brushstrokes due to the size of the thumbnail. Is this seriously the standard CC interface? Its completely counterproductive. Please just tell me this isn't the new standard? Anyone else have the same issue?
agreed this is a real problem. The brush preview should be replaced with previous version.
I think this is the stupidest design change of Photoshop CC.
Brush preview window is practically useless now, and it makes me impossible to create new brushes.
I hope them to restore old-and-good large preview back.