you will be able to add these using a standard extension mechanism soon. A set of features to customize the palette is currently under development. Tracking issue is here: http://jira.codehaus.org/browse/ACT-278 If you take a look at Tom Baeyens' and Joram Barrez' Devoxx presentation from last week, you can see a slide with an example of how that will look in the designer. The presentation is here: http://slidesha.re/cUuprf
there is no fix version for that issue, so technically, I can't say at the moment. Particularly in the runtime part we have some work left to do. If you want to get started with creating some basic own node types with simple properties (but not executing), you will be able to do so with the next release of the designer, which should be available mid December.