As some of you know, this list that's up on the RPH Help page is missing a lot of the skyboxes that are actually in the later expansions such as MoP, WoD and Legion. When searching for any of the zones from those expansions in .lo sky, nothing comes up like it did when the feature was first introduced. Although this macro won't specify what region the skybox is from, it will provide the ID for that skybox.
First macro: This simply provides a starting value for the IDs. For example, based on the RPH list, a lot of values between 4000-8000 are missing, so set the starting value at 4000 which is about where MoP skyboxes are.
Second macro: The actual command that will go through the skyboxes. The first line will state the ID. The second line is the command. The third line will increase the value by one every time.
/script SendChatMessage("Skybox: ".. i .."") /script SendChatMessage(".ph sky ".. i .."") /script i=i+1
Write down any cool skybox IDs you come across that you want to use for your phases and enjoy!