Hi and welcome to this forum,

A sequencer is usually a nice project, particularly if you are a beginner (you didn't mention your level of skills in Pd). See for instance this chapter of Kreidler's book: http://pd-tutorial.com/english/ch04s02.html

Designing Sound by Andy Farnell is also excellent and has some nice examples of generative video game sounds created in Pd. That could inspire you for some project. Check out some of his examples at http://obiwannabe.co.uk/

You can also check Pure Data's channel on VIMEO for some inspiration:

Cheers,
Gilberto

The nice thing about PD is that if you keep soft eyes on it, you'll start working on something just to realize there's something better to work on, and in the end, hopefully, you'll spend your whole life writing different patches to try to fulfill the same musical idea...

@pdedel May I suggest taking a look at the pdpatchrepo:
http://www.pdpatchrepo.info/patches

Cheers~