I have played Oblivion for several months now, and the most annoying thing that I have seen so far is that all the temples are very, well, cookie cutter. I was wondering if there was a mod which would make each temple look different, and maybe, make them a bit more, well, interesting.

I do not think so, but I think you might find http://www.tesnexus.com/downloads/file.php?id=29580 nice to look around. I found http://www.tesnexus.com/downloads/file.php?id=14547 you may want to check out while searching for Floydian1's.

...maybe a http://www.tesnexus.com/downloads/file.php?id=15743? http://www.tesnexus.com/downloads/file.php?id=7361 for refuge?...http://www.tesnexus.com/downloads/search.php?name=chapel&scid=20&author=&mname=&desc=&size1=&size2=&downloads1=&downloads2=&udate1_day=&udate1_month=&udate1_year=&udate2_day=&udate2_month=&udate2_year=&ldate1_day=&ldate1_month=&ldate1_year=&ldate2_day=&ldate2_month=&ldate2_year=&endorsemants=&images=&readme=&advltonly=&page=1&orderby=name&order=ASC...http://www.tesnexus.com/downloads/search.php?name=Temple&scid=20&author=&mname=&desc=&size1=&size2=&downloads1=&downloads2=&udate1_day=&udate1_month=&udate1_year=&udate2_day=&udate2_month=&udate2_year=&ldate1_day=&ldate1_month=&ldate1_year=&ldate2_day=&ldate2_month=&ldate2_year=&endorsemants=&images=&readme=&advltonly=&page=1&orderby=name&order=ASC (some nice temple additions there, after first page)...

Yes there are:

http://www.tesnexus.com/downloads/file.php?id=26000 (adds statues of the appropriate god to each chapel); and

http://www.tesnexus.com/downloads/file.php?id=10019 (changes the windows so the appropriate god is featured over the altar).

Those are just from a quick search through my archive.

I saw that first one in the "chapels" search, but that second one is an interesting find...