Praise be to Allah, the Lord of the World.
Mummification of an animal involves taking out its intestines and stuffing it with chemicals to prevent decay and preserve natural form. Mummified animals are of two types.
First: animals whose meat is lawful, such as camels, cows, sheep and some birds. Mostly, people don`t mummify this type because doing so is a waste of money and they benefit from every part.
Second: animals whose meat is unlawful, such as dogs, lions, falcons and the like. Lawful animals, which were not slaughtered according to ritual requirements or were forbidden to eat such as dogs and were slaughtered or died, they are dead and impure. Ibn An-Naqeeb says: "Impure things are urine and feces…..animals whose meat is uneatable when slaughtered and the dead animal except fish….also the hair of the dead or the uneatable animal. The meat of all these is impure." [Umdat as-Salik,( pp.71].
Buying and selling dead animals is forbidden because Jabir bin `Abdullah narrated that he heard Allah's Messenger (PBUH)
in the year of the Conquest of Mecca, saying: "Allah and His Apostle made illegal the trade of alcohol, dead animals, pigs and idols."{Related by Bukhari & Muslim}. "It is impermissible to sell an impure item whether it was possible or impossible to make pure by changing its chemical composition, such as the skin of the dead animal."{Tohfat al-Habib ala-Shareh al-Khatib, 3/9}. According to our Madhab, Shafie, the general maxim is that it is prohibited to kill animals except the harmful, because Islamic Law forbids killing animals for no need, save for food. By virtue of this, exemplary punishment is prohibited as well. Al-Bayhaqi has dedicated a whole chapter in his book, [Al-Sunnan al-Kubra], entitled: "Prohibition of killing animates save for food." He added the Hadith in which Abu Baker gave an advice to the soldiers leaving to Sham (Syria) where he told them: "Do not slaughter sheep or camels except for food.(Al-Sunnan al-Kubra, vol.9, pp.86).
Imam Tabarani related in [Al-Mou`jam al-Awsat]: "The Prophet (PBUH) forbade exemplary killing." Ibn Hajar said: "He ordered that if we kill, we kill well and forbade exemplary killing." {Fateh al-Bari, vol.5, pp.42}.
Moreover, it is clearly forbidden to hang mummified animals on the wall for decorative purposes, because they are animates. This clear prohibition is reflected in the Hadith in which `Aisha narrated: "I stuffed for the Prophet (PBUH) a pillow decorated with pictures (of animals) which looked like a Namruqa (i.e. a small cushion). He came and stood among the people with excitement apparent on his face. I said: "O Allah's Messenger (PBUH)! What is wrong?" He said: "What is this pillow?" I said: "I have prepared this pillow for you, so that you may recline on it." He said: "Don't you know that angels do not enter a house wherein there are pictures; and whoever makes a picture will be punished on the Day of Resurrection and will be asked to give life to (what he has created)?" {Related by Bukhari}.
Also, Abu Talhah (May Allah be pleased with him) said: "The Messenger of Allah (PBUH) said: "The angels do not enter a house in which there is a dog or a portrait." [Al-Bukhari and Muslim].
In conclusion, based on the above, we are of the view that it is forbidden to mummify animals for decorative purposes. And Allah the Almighty Knows Best.