For comparison, I looked up the guestlist of official delegations at the funeral of Pope John Paul II (the last pope to die in office) in 2005:
The royal guests included:
Predominantly Catholic countries
Andorra: H.E. Bishop Joan Enric Vives Sicilia, Co-Prince
Belgium: Their Majesties the King and Queen of the Belgians
Liechtenstein: H.R.H. Reigning Prince Hans-Adam III of Liechtenstein and his Consort
H.R.H. Princess Marie of Liechtenstein, H.R.H. Prince Nikolaus of Liechtenstein, Ambassador to the Holy See, and his Consort, H.R.H. Princess Margaretha of Liechtenstein
Luxembourg: H.R.H. Grand Duke Henri of Luxembourg and his Consort, H.R.H. Grand Duchess Maria Teresa
Spain: Their Majesties the King and Queen of Spain
There was no official royal representation from Monaco.
Predominantly Christian (but not Catholic) countries
Denmark: H.M. Queen Margrethe II and H.R.H. The Prince Consort
Georgia: H.R.H. Princess Khétévane Bagration de Moukhrani, Ambassador to the Holy See, with her Consort
Great Britain: H.R.H. The Prince of Wales
Lesotho: H.M. King Letsie III
Norway: H.M. Queen Sonja of Norway
Romania: H.M. Michael I
Sweden: Their Majesties King Carl XVI Gustav and Queen Silvia
There was no official royal representation from the Netherlands, Samoa, Swaziland, or Tonga.
Predominantly Muslim countries
Jordan: Their Majesties the King and Queen of Jordan, H.R.H. Prince Ali bin Al Hussein, H.R.H. Prince Ghazi bin Mohammed
Kuwait: H.E. Sheikh Jaber Al-Abdullah Al-Sabah, H.E. Sheikh Michaal Jaber Al-Abdullah Al-Jaber Al-Sabah
Morocco: H.R.H. Prince Moulay Rachid
Oman: H.E. Sheikh Abdulla bin Mohamed Al-Salmi, Minister of Religious Affairs,
H.E. Sheikh Abdulla bin Salim Al-Rawas, Minister of the Regional Municipalities, of the Environment and of Water Resources
Qatar: H.E. Sheikh Tamim Bin Hamad Al Thani, Crown Prince, Vice-Emir of Qatar
United Arab Emirates: H.R.H. Sheikh Abdulla Bin Zayed Al Nayahn, Minister of Information and Culture
There was no official royal representation from Bahrain, Brunei, Malaysia, or Saudi Arabia.
There was also no official royal representation from the monarchies of the non-Christian non-Muslim countries of Bhutan, Cambodia, Japan, or Thailand.