There are no unintended consequences, because there are no rules for dead creatures, so all interactions are up to the DM.
Death is not a status effect. There are no stats for dead bodies, no special rules concerning them. Nothing describes what happens, mechanically, to a creature after they die.
The reason for this is because death is universal. There's no need to explain what being dead means to anyone, so it isn't explained. Because of this, any questions that do come up are left to the DM.
That said, I'll go over a few of the likely suspects:
Cure Wounds, or any kind of healing (outside of explicit resurrection) has no effect. Being dead is not a result of being at 0 hit points, so even if casting a healing spell on a body is possible, it wouldn't bring them back to life. It could be argued that their body would be healed, but all resurrection methods specify the HP total the creature returns to, so DM fiat would be required for this to even have any effect.
Dominate Person and other such enchantments all require wisdom saving throws. There are no rules provided for what the wisdom save of a dead person is, but even assuming that translates into an automatic failure, a dead person can't move or do anything whatsoever, so such control would be entirely pointless.
Teleport, and other spells that specify "willing creatures" can't target a body because dead creatures are not willing creatures. They're dead, and thus unable to perform the positive action of being willing.
Sacred Flame and other creature-targeting damage spells. This would technically be a change, as you can now attack corpses, however there is no shortage of ways to attack objects, and having a few new ones doesn't really change anything.
Sneak attack, while not a spell, could be argued to work if your dead ally was adjacent to your target. However, the adjacent creature need to be "hostile", which is again an positive action much like being "willing". Dead creatures can't do anything, so they can't be hostile.
At the end of the day, due to the lack of rules concerning death and dead bodies, any possible strange interaction that might arise from dead creatures being considered creatures is up to the DM to decide. And since the DM is deciding every consequence, there are no unintended consequences.