We have been using octopack and teamcity for ages to package wpf apps, never notice that with a default nuspec or just the csproj file, it includes the obj folder which contains all the binary xaml (baml) and generated code behind cs files.
A quick solution is adding a explicit nuspec file that only includes the bin\release folder
<files>
<file src="bin\Release\**\*.*" target="" />
</files>