There are several `pic-[mathtype]` options, see [1]. pic-equation requests images for equations, but it doesn't include TeX code in the alt attribute, it seems that it is derived from the DVI code by the tex4ht command.

To get TeX in the alt attribute, we would need to fetch the whole math content, and use it twice. One time to typeset it, the second time to save it in the alt attribute, using token register or `\detokenize` command. It seems that `pic-m+` option does that, but only for `$...$` and `$$...$$`. The configurations for `\(...\)` and `\[...\]` are commented out in the literate sources. And there is also "not safe!!" comment, so I guess that it has some issues. But it works for me on some basic samples.

It seems that GladTeX processes the HTML page for LaTeX code, so it should work if we leave the math unprocessed. There is a support for that in one package from Helpers4ht bundle [2]. It uses verbatim to support environments like equation or align.

Personally, I am more interested in Mathjax-node [3], because it can convert MathML to the plain HTML+CSS, with correct rendering in both Firefox and Webkit based browsers. Basically, it is rendered in the same way as if Mathjax was used, but the loading is much faster, because no Javascript processing is involved.

[1] http://cvr.cc/?p=504
[2] https://github.com/michal-h21/helpers4ht/blob/master/mathjax-latex-4ht.sty
[3] https://github.com/mathjax/MathJax-node