I didn't see this question, or I would have responded earlier. Many apologies.
At the moment, both "report" and "online" are undefined by biblatex-mla. For all of my own needs, I've never previously cited a website that couldn't be conceived of as an article, but I can see the worth. "Online," at least, could very easily be defined in the next version of biblatex-mla.
"Report" is another problem altogether. The MLA conceives of governmental authorship as if it were a nesting doll. Something by the "Department of Unusual Citations" in the US Senate would be cited like this:
United States. Cong. Senate. Dept. of Unusual Citations. Italicized Title. Washington: GPO, 2011. Print.
The next entry, by the House's "Bureau of Oddities" would look like this:
---.---. House. Bureau of Oddities. Italicized Title. Washington: GPO, 2011. Print.
You can see where things start becoming too much to handle. If Biblatex-mla is able to handle everything else you need, at the moment I'd recommend defining your report as a "book" with the author in your .bib file defined within curled braces. I don't want to release support for governmental publications unless I can do it correctly, that way my users understand the limitations of the software. With the recent innovations in Biblatex and Biber, I'll be looking closer at this problem to see if it's one I'll soon be able to solve.