I would not recommend using this block any more unless your design requirements are extremely minimal. In general, I think you will be much happier using JordanLev's Designer Content block instead (it's free too!). You can find out more about it here.
This custom block relies heavily on the code for the standard C5 block types: 'content' and 'image'. The user specifies the image separately from the wysiwyg content, then makes other settings.
The other settings currently include the image alignment (left or right), an optional caption (displayed below the image), a url to make the image a link (with a switch to make it open in a new tab) and finally alt text.
Besides making it easy for the user to get things to line up and wrap correctly (with reasonable margins), this block resizes the image based on the specified max width and height so we get nice small files.
I've tested in a couple of themes and stacking these blocks seems to work fine, with no big gaps between them. The content and image are followed by a clearing div, so the float doesn't break the layout.
There's a truly tiny view.css file that can be edited to change the caption alignment, font-style, etc.
Currently, one limitation is that you can't add file download links to the content area using the 'Files' button on the concrete5 toolbar at the top of the content editor. If you need your content to contain a link to a file, a workaround is to add a temporary content block with the links you need, then copy/paste the links into the 'Content Around Image' block.