Right, title is not deprecated - but "alt" is required for valid (X)HTML. It is intended for readers that do not render images (such as search engines*) and to assist those who can't see images (screen readers for the blind, for example.) A screen reader will read aloud "Company logo". Just a two or three word description of what's in that image (* again! :-) )
Many designers eliminate them or leave them empty because they don't like it when text pops up over their images. Your pages will be fine without them, and an empty alt still validates. When you go to insert images in W.P., there is a field for the alt attribute. You can populate it from there.
* If you have no other motivation for using the alt attribute: since alt's are indeed read by search engines, they can assist white hat SEO strategies. Don't stuff them with keywords, keep it relevant, but it does help.