The internet is full of 'Midi files'. These files can be opened with your version of Mixcraft or, in fact, any other DAW (Digital Audio Workstation) that can import Midi files.
Treat a Midi file as a project file. As an example, you can download any Midi file from this page: http://www.garyrog.50megs.com/midi1.html
Then, open it as a project file. Once opened, you should have several tracks which can be edited to your liking, and then saved out as a proper Mixcraft project file.
Even if you don't want to edit these files (for example: changing the instruments of the tracks or adding reverbs, EQ and compressors etc.) you can have a ton of fun just playing them back through Mixcraft.
Midi is a standard created in 1983 that allows midi devices (such as keyboards, synths and modules) to talk to each other, as well as allowing creators of midi files to work to a standard; for example, reserving track 10 for drums or Controller #1 for modulation. During the 80's and 90's, I worked extensively with the GM, GS & XG Midi standards to produce professional midi files.https://www.midi.org/specifications
If you want to learn more about Midi there are tons of articles online, start here: https://en.wikipedia.org/wiki/MIDI
or here: http://www.midiworld.com
So, if you want more music for your DAW, try Midi. You won't be blown away by great sounding tracks, but with a little bit of work you can improve on how these tracks sound.
Finally, be aware that although these files can be found in abundance on the internet they may very well be copyrighted by a company or the individual who produced them. If you re-post these files online, then please give credit where it is due.