{dvi} should be used for questions about the DeVice Independent format produced by the classic (la)tex compiler. If the question is about how to produce a dvi file with the classic (la)tex compiler then the tag {dvi-mode} should be used instead.
DVI is the DeVice Independent format produced by the classic tex and latex compilers, which is then usual converted to (E)PS and/or PDF. Only EPS files are supported as images. The more modern pdf(la)tex compiler produces PDF output directly and supports PNG, JPEG and PDF images.
Note that the tag dvi-mode should be used instead for questions regarding the class latex compiler which produces DVI files. This tag is equivalent to pdftex while dvi is equivalent to pdf.
See How to tag questions specifically about the classic DVI-producing latex compiler? for the discussion dvi versus dvi-mode.
