to exclude filetypes from searches in Limewire go to:

Tools --> Options --> Filters --> Keywords

Then add e.g. .rar (remember the period) rar will not be as effective or too effective as it will block any file that has rar anywhere in the filename.

Then press Apply and OK

Now no .rar file will show up anymore

As for the filesizefilter, we're all hoping and praying that it will be added soon