There are two separate issues:

1. LuaLaTeX is failing to include png and other bitmap formats in dvi mode. These formats aren't normally supported by dvi, but only warning should be printed, as in the case of normal LaTeX. This should be fixed in graphicx's driver for LuaLaTeX.

2. As tex4ht uses own dvi driver which supports additional picture types, it should provide support for them. We could provide own graphicx configuration file, but it seems like too heavyweight solution to me . Or we can use similar configurations :)

It fixes also problem with image size detection for bitmap images with other engines, so while it is hack to fix lualatex support, it also enhances experience with standard htlatex, otherwise the user needs to either use different backend for graphichx with tex4ht, or provide similar configurations in the .cfg file.

With this change, only .xbb files need to be created for images and then their correct dimensions are used in the html.

This is an crosspost from http://tex.stackexchange.com/q/255220/2891. The problem shows when we try to include some image in format which is not supported in dvi mode:

\documentclass{article}
\usepackage{graphicx}

\begin{document}
\includegraphics{someimage.png}
\end{document}

It turns out that graphicx package tries to find the bounding box of the image. It tries that by reading the image data. But because images are binary, this cause LuaLaTeX to complain about incorrect utf8 value. It easily exceeds 100 errors and the document fails to compile.

David Carlisle proposed a solution using \DeclareGraphicsRule:

\DeclareGraphicsRule{.png}{bmp}{.xbb}{}
\DeclareGraphicsRule{.jpg}{bmp}{.xbb}{}
\DeclareGraphicsRule{.gif}{bmp}{.xbb}{}

with this code, images aren't parsed for the bounding box, but .xbb files are used instead. They can be created using

ebb -x imagename

This solution fixes also behavior with normal LaTeX, as bounding boxes weren't loaded with it as well.

More details are provided in my answer to the question on TeX.sx

Patch for literate sources is attached.