I usually try to include some reference to the Table Name that the layout uses. For example, I may call a layout Customer Detail if it is based on the Customer table.
The Detail portion of the layout name leads to my second preference, which is to specify what kind of view mode is this layout supposed to be (Detail or Form, List, Table)
Finally, like you, if my layout is meant for iPhone or iPad, I will have that there too.
So, for a layout that is based on the Customer table and will be used on the iPad, I may call it "Customer Detail - iPad"
I did plan to add a comment on filemakerstandards.org, but couldn't find how to join or otherwise participate (only to log in). Could you point me to some instructions?