Towards the end of the document that pandy linked to, there is the following list of workarounds that do not involve changing the doctype:
- Any image alone in a table cell (e.g., single-pixel spacer images) should be made block-level.
- Any image in a table cell with other images should be vertically aligned with the bottom of the line box.
- Any image in a table cell with other images and text should have its vertical alignment changed as necessary, if at all.