Go to Images and Media / "Insert file" dialog in WikiEditor.

Plz change labels in "alignment" box, to reflect actual behavior:

Change:
"left" to "Left, wrap text on right"
"right" to "Right, wrap text on left"
"none" to "Left, no text wrap"
etc

Or, have separate checkbox for "wrap text", so that user can choose any alignment with or without wrapped text. That would be best of all. Otherwise, images overlap into sections below them. For example, i cannot select "Thumb" format without images overlapping into next section on the page. Severe limitation.