One minor annoyance of TinyMCE (and most WYSIWYG) editors is that the standard alignment option for images uses the "align" attribute on the <img> tag. This, unfortunately, tends to look butt ugly. So most of us end up creating custom styles for alignment (float: right, etc) and training our clients to ignore the Alignment option and use the Class option instead.
Some of our clients are not this bright.
Thus, I’ve come up with a little technique that overrides the "align" attribute with the CSS style of your choosing. Easy for the client to set, but you control what it looks like. Since this works beyond MODx, I’ve posted a tutorial here:
Overriding alignment in <img> tags
Hope you find this useful. Viva MODx!
Andrew