As floating images are not supported yet, there is only one option and it will only work out if the rich text box is read only and you are not changing the layout mode, margins, etc. of the document. That would be to create a table with 2 or 3 columns (depending on the position of the image - on one of the sides or in the middle of the text) and put the image in a separate cell, while the text is in the adjacent cells. You would have to find experimentally how much text should fit into the cell on the right and when you should continue with the cell bellow.
We have floating images on our to-do list, but I cannot provide you with a specific timeline of when they are going to be implemented. We agree that it would be a nice amelioration, but we have some other nice features scheduled for Q1 2011, which are of higher priority. I am creating a PITS issue, which you can use to track our progress on this one: PITS issue URL.