The actual executable file is contained inside the bundle (like bundles in an OS X application's package). The bundle is really just a way of packaging all your resources together and it's size shouldn't affect your application's load time. Those resources aren't getting loaded when the app is run (unless you are doing something to load them).
http://developer.apple.com/library/mac/#documentation/CoreFoundation/Conceptual/CFBundles/AboutBundles/AboutBundles.html
A bundle is really just a directory:
A bundle is a directory with a
standardized hierarchical structure
that holds executable code and the
resources used by that code.
And you should include all of your images:
Applications should always include all
of the images, strings files,
localizable resources, and plug-ins
that they need to operate [inside the
bundle]. Noncritical resources should
similarly be stored inside the
application bundle whenever possible
but may be placed outside the bundle
if needed. For more information about
the bundle structure of applications,
see “Application Bundles.”