New Post: Need help with MSFProj

As for adding file types - you have to add Item Template for every type you wish to support. For instance, for text file you should add a vs template (as well as __TemplateIcon.ico and TextFile.txt file) like this:

<VSTemplate Version="2.0.0" Type="Item" xmlns="http://schemas.microsoft.com/developer/vstemplate/2005">
  <TemplateData>
    <DefaultName>TextFile.txt</DefaultName>
    <Name>Text File</Name>
    <Description>An empty text file</Description>
    <Icon>__TemplateIcon.ico</Icon>
    <ProjectType>[string which is your project type from ProvideProjectFactory attribute]</ProjectType>
    <SortOrder>50</SortOrder>
  </TemplateData>
  <TemplateContent>
    <ProjectItem>TextFile.txt</ProjectItem>
  </TemplateContent>
</VSTemplate>

In your custom ProjectNode class you create items and folders via these overridden methods:

        protected internal override FolderNode CreateFolderNode(string path, ProjectElement item)
        {
            if (item == null)
            {
                throw new ArgumentNullException("item");
            }

            return new CustomFolderNode(this, path, item);
        }

        public override FileNode CreateFileNode(ProjectElement item)
        {
            if (item == null)
            {
                throw new ArgumentNullException("item");
            }

            return new CustomFileNode(this, item);
        }