can i use iCloud instead of MobileMe?

For what?

iCloud can be used to sync your documents between iCloud-ready applications to your mobile devices, but you cannot use it to host web galleries. For this you will need to find a different host, for example the ftp-site of your internet provider. Export your web galleries to your hard drive and upload them to your new web host using ftp (I use Cyber Duck for this).

See Roger Wilmut's page (the last line on the page addresses links to photo galleries):

Migrating from Mobile Me:

http://www.wilmut.webspace.virginmedia.com/notes/migrate/frommobileme3.html

And if you need a replacement for your iDisk, see this user tip by Winston Churchill:

Winston Churchill: Using iCloud as an iDisk:

https://discussions.apple.com/docs/DOC-2711

If you create your web pages with iWeb, you can still use the iWeb application, but you need to patch it a little, because iWeb references icons (arrows) on MobileMe, that may not longer exist: See this guide by Old Toad and Roddy, on how to do this:

Modify the iWeb Application: http://oldtoadstutorials.net/No.26.html

Regards

Léonie