There are various different types of Arcade classics....

For example. You can have your main MAME build brought to you on the wheel in theme either with "Arcade Classic" visuals or with "MAME" visuals, this is just the entire collection brought you you with 2 dif types of artwork. I like to use "Arcade Classics" for the main wheel as anyone who knows nothing about computers has no idea what MAME is. They prob think its a horses hair emulator 

If you want to then, like me you can get a bit more detailed with other wheels. An example of this would be to have another MAME wheel setup with only say for example Nintendo games. You could then get artwork for this to make a "Nintendo Classics" wheel. This can then be done for various other types of games within the same MAME collection. The only thing changing is the XML it chooses to pick the roms and the artwork.

You could then go one stage further. For example have a Capcom only wheel. These games are all found in the MAME database. But however you want to change the visuals and, cntrols or something lik that. You could then use a complete dif emulator to make this work. For the "Capcom Classics" wheel only you could use for example the Final Burn Alpha Emulator to run them. Same principles as above just getting a little more advanced. Its a good way to recycle your roms in various ways. Be aware however MAME is a untamed beast... with me anyways. There are so many dif versions etc that to start linking the same games to dif emulators can get complicated. In most cases it may be worth downloading a set of roms just for that emulator... for example "Zinc"

This could then go on with all kinds of different changes. Your only limited to your own imagination, 

The classic collections just specific system collections parsed out of the mame directory. This is done by having their own databases and media folders that include sorted out wheel images. The games and videos are set up to come from the mame directorys.

This is just a quick overview.

Good luck!