Finding specific types of files only

I would love to the feature where we could do a search for only specific files but not based on titles, names or tag. Based purely on the kind of file it is. For example, only .jpeg or .jpg, only .eps, only .key and so forth.

I'm a photographer and there are times when I just plain don't know where a file is or have no clue what I called it. But I do know I created it in Photoshop and it is a .PSD file. 

I should be able to do a search and only find .PSD files. Then maybe further restrict the search to a specific time range.

I have to say this, I can do this in Google Drive and was surprised to learn there was no tool in Dropbox to handle the same.