Since all my faxes come in as TIF ( direct import from Hyalfax ), I needed a tif viewer. Using the browser was no good as there is no default tif viewing mode. So, I'm using the free brava reader at http://www.bravaviewer.com/reader.htm which seems pretty good. Keyboard control of rotation for those faxes that come upside down and thumbnails as well. And it doesn't lock the file so it can be deleted while the viewer is viewing it .. for fax spam.
Ideally there would be a .tif .jpg .pdf .whatever.we.want viewer / editor to meet our needs. Nothing wrong with paying some money to get a good viewer.
There is http://www.irfanview.com/ which is freeware and supports dicom images as well. I have not tried it though ...