The new clamwin has a feature to scan only executable files. However, if I have understood well, this feature skip files with file type CL_TYPE_SKIP, as defined here:
https://clamwin.svn.sourceforge.net/viewvc/clamwin/trunk/clamav-devel/libclamav/filetypes.c?view=markup
keeping on scanning all other files.

What about doing a multi-level selection of how to scan?
1) Scan all files (as in pre-0.90);
2) Scan all files, execpt that marked as CL_TYPE_SKIP (so also CL_TYPE_UNKNOWN_DATA, as in post-0.90);
3) Scan only know files, excluding CL_TYPE_SKIP and CL_TYPE_UNKNOWN_DATA;
4) Like 3) but excluding "File that may contain exploits against MS systems";

The default should be 2), but the user should be able to select the others options to improve scanning time.

not so easy to implement, the code to do this is sparse around clamav sources

Do a search on Google for "dangerous file extensions." Use Filters on the ClamWin to check for these file types via the Preferences menu. I do this, and also add pdf, doc, xl*, ppt, pub, dll, sys, php, and a few of the most commonly used compression file extensons. I also exclude the following files: cab, msi, msp, chm, dat, mp3, mpg, jpg, wav, wmf. It takes ClamWin about 35 minutes to scan the 180 GB hard drive on my Win XP machine.

I know this isn't perfect, but I also use another antivirus with a real-time/resident scanner. I feel adequately protected, but if you are using only ClamWin, it might be better to scan everything.

Regards,