Does Pure Land Buddhism ever have a Buddha other than Amitābha as the object of devotion? Or is Pure Land Buddhism by definition a devotion to Amitābha and an aspiration to be reborn in his pure land? I'm aware there are a lot of other Buddhas so I just wondered if they were ever the focus of this tradition.
Yes, there is other Pure Land in Buddhism other than Amitabha Buddha's. It is called the Pure Land of Lapis Lazuli of the East. The Buddha that resides there is called Bhaisajyaguru Buddha or Medicine Master Buddha of Vaidurya Light. In order to achieve rebirth there, one must practice the recitation of the Buddha's name. For the rest of one's life.
In Jodo Shu and Jodo Shinshu, Amitabha Buddha is the sole object of devotion, because to be devoted to Amitabha Buddha is seen to be devoted to all the Buddhas, in spirit and practice. Reciting Nembutsu is seen as fulfilling the aspirations of all the Buddhas, including Shakayamuni and Avalokitesvara.
From "What Kind of Buddha Is Amitabha?", A Discourse by Dharma Master Huijing, Xiamen, China; October 2006:
Moreover, to recite the name of a single Buddha, Namo Amitabha Buddha, is equivalent to reciting the names of all Buddhas. When we recite Amitabha’s name, the Buddhas of the ten directions will come to praise, protect and encourage us. So there is great wisdom in choosing to practice this teaching.
After we learn this practice, there is no further need to recite the names of Bodhisattvas Avalokitesvara and Mahasthamaprapta. If we only recited Amitabha Buddha’s name, Avalokitesvara and Mahasthamaprapta would happily become our friends, even brothers. They will safeguard us, the way a shadow follows the form that cast it. For the name we recite is the name of the one who sits on top of their heads.
We should realize that Bodhisattva Avalokitesvara’s goal is to guide suffering beings to recite the name of Amitabha Buddha, who will deliver them to the Pure Land. Otherwise, Avalokitesvara would be saying, “How tired I am! You are still reincarnating and suffering. Lifetime after lifetime, again and again, I still have to save you from pain and peril. But if you recite ‘Namo Amitabha Buddha’ this very lifetime, I can relax!” That’s the aim of Bodhisattva Avalokitesvara.
Individuals in other Pureland sects throughout East Asia revere other Buddhas. But, if you notice, my quote above is taken from a modern day Chinese master. This is because some Chinese Pureland masters reference the works of Master Shandao, the Chinese Master whose work was translated into Japanese and inspired the Jodo Shu and Jodo Shinshu sects (he taught exclusive Amida recitation). Some masters are making an effort to return this teaching and legacy to places like China and Taiwan.
In the same essay I quoted above, you can find this idea:
...So our school is not some Japanese Pure Land school. Our school of the Fundamental Vow teaches the 18th Vow of Amitabha Buddha. What does the 18th Vow say? It speaks only of Amitabha-recitation. Master Shandao said, “Shakyamuni Buddha’s underlying wish is none other than for beings to recite the name of Amitabha single-mindedly and exclusively.” The 18th Vow is called the Fundamental Vow. Thus “Amitabha-recitation, according to the Fundamental Vow” was taught and transmitted by Master Shandao.
What is the purpose of the Fundamental Vow? And what is the reason for Amitabha’s attainment of Buddhahood? The goal is that all sentient beings can be reborn in the Land of Bliss merely by reciting Amitabha’s name. Therefore “Shakyamuni Buddha’s underlying wish is none other than for beings to recite the name of Amitabha exclusively.” Recitation of Amitabha Buddha’s Great Name of a Myriad Virtues is specified in the Fundamental Vow; it is also the only practice mentioned there.
So, it all depends on what practice someone chooses.
Short answer, no. Although we revere Sakyamuni, he is not the focus of Pureland. However, the devotion to bodhisattvas is something else. Mainly, there is Kuan Shih Yin Pusa, Ta Shih Chi Pusa, and the rest of the "ocean-wide lotus-pond assembly" of bodhisattvas in the Pureland.
While there are other Buddhas in other pure lands, and people have paid reverence to them, that is not the definition of what we call Pureland Buddhism. Rather, that would be a secondary practice. Or it might even be part of Vajrayana Buddhism.