Well, if you ask me, I dont use just any one webhost. For design, I use Geocities, no HTML of course for their basic designer, & you can make it virtually in any way you want.
They also allow for you to add pictures & files, as long as they are yours & you own the rights to them. If I am going to upload pics for avatars, I use angelfire, it works on most peoples computers, but people behind firewalls miss out on it so I hear.
However, I doubt you will be able to make a commercial demo, within a few megs by todays standards, so if you cant get it below 5 megs, I would serriously consider buying some webspace & uploading it via FTP.
I can recomend the one from DTAGames, fairly cheap for a webservice, at the size that they give, & a lot more. Just goto
http://www.dtagames.com & look at their webhost section off of their main page.
Im going to be buying the website hosting sometime soon hopefully, & get a registered domain & some other stuff. From last I checked, it will cost about $100 per year to host, with domain, which is fairly cheap in todays world.
Anyway, if you cant do that, think about getting your demo/game hosted on a place like gamespy. I belive they will setup mirrors for your games, if you submit it & they approve it.
I hope this can help you out some,