You have the basics of how HyperSpin works... It works just like any other front end out there. When you launch HyperSpin it plays an intro video (this can be turned on/off). The first menu that comes up is the Main Menu. The main menu contains those systems that you want to be able to select from. Each system on the Main Menu has a theme created for it that is specific to that system. You can change these themes or create new themes as you see fit.
This video is a bit outdated, but this is an example of System Themes (Aka Main Menu) in HyperSpin:
[youtube]http://www.youtube.com/watch?v=XyIDeUE9aGk[/youtube]
Once you select a system this takes you to the game menu, just like any other front end out there. However, HyperSpin allows you to have a generic, what we call a "default" theme. This theme will appear for any game that you do not have a specific game theme for. I personally use default themes for most consoles like Nintendo, Sega, etc... We have complete theme sets for some systems such as Daphne where each game has it's own theme. Select Dragon's Lair and you see a Dragon's Lair theme, move down to Space Ace and you see a Space Ace theme. From there you hit your designated start button to enter the selected game.
For MAME, and any other system out there, we have what we call Game Specific Themes. Game Specific themes are themes that has been created for a specific game. You select Battletoads you'll see the Battletoads artwork/theme for that game, move to Street Fighter 2 and you'll see specific artwork/theme for Street Fighter 2.
This is also an old video. Once you select a system from the system theme/Main Menu (see previous video) you are taken to the game menu. The video below is of Game Specific themes. What you don't see in this video are default themes. Default themes were implemented after these demo videos were taken.
[youtube]http://www.youtube.com/watch?v=lEgaqXsavYA[/youtube]
Not every game has artwork though and we haven't been able to create a theme for every game yet, but for those games... You can either set the front end to display only those games that you have a game specific theme for OR you can mix game themes with default themes. If you have a game theme for a game then when that game is selected then you'll see the theme for that game. If you move to a game that does not have a game specific theme then this is where the default theme comes into play. You'll see the default theme instead of a game theme since one is not available yet. So, yes a different theme can pop up when you scroll through the game OR you can have a SET theme for the whole kit-n-kabodle. When it comes to themes HyperSpin is by far the most robust and flexible front end out there.
If you want a one theme setup, like Maximus, then that is possible as well. However it really takes away from what HyperSpin is really capable of.
Download the main package. It contains most of the stuff to get you started... Main Menu and some default themes. You will have to provide your roms and emulators as these DO NOT COME with HyperSpin.