Adding modified or new text files to my PPA package is simple enough:

Step 1:

apt-get source [foo-package]

cd [foo-package]

Step 2:
add or modify new text files containing the changes

Step 3 - update the changelog:

dch -i

Step 4 - create a patch

dpkg-source --commit

Step 5 - create a source package

debuild -S 

Step 6 - upload to launchpad

cd ..

dput [myppa]/[foo_source.changes]

However, I now need to add a new icon file (a .png file) to the existing package.

So at step 2 - just copied into the [foo-package]

At step 4 - I get the following errors:

dpkg-source: error: cannot represent change to foo-package/foo-icon.png: binary file contents changed

dpkg-source: error: unrepresentable changes to source

If I attempt to move to step 5 I get the following additional errors to the above:

dpkg-source: error: add foo-package/foo-icon.png in debian/source/include-binaries if you want to store the modified binary in the Debian tar-ball

...

dpkg-buildpackage -rfakeroot -d -us -uc -S failed

Any ideas how do I add a binary icon file to my existing PPA package?

More information

By running:

debuild -S --source-option=--include-binaries

This then allows for the source package to be built and step 6 is possible.

However this isnt really the answer - because I subsequently cannot then make further code changes (step 2) because I'm still getting the same errors.

It doesnt look like I can do dpkg-source --commit --source-option=--include-binaries because this just gives errors:

dpkg-source --commit --source-option=--include-binaries

dpkg-source: warning: --source-option=--include-binaries is not a valid option for Dpkg::Source::Package::V3::quilt

dpkg-source: error: cannot represent change to foo-package/foo-icon.png: binary file contents changed

dpkg-source: error: unrepresentable changes to source