Hey mate, awesome plugin, I love it!
One thing that I think would really improve it would be if you could make it so that you can specify the author of posts you want to return, just like how you can do this with categories or tags. For example, if I could do this:
[ic_add_posts author='author-slug or ID' showposts='50']
Just a thought! I'm not sure if it's possible but it would be really useful!