1- Timers
It's okay to have 1000 timers in your project but it's not okay to make the timers interval too low (Ex: 5ms or 10ms)
Also you need to make sure that they are working async without effecting the UI which would also cause memory leak
2- Images
Loading too many images without giving the time for the Android-IOS-PC (OS) to call the garbage collector is also a no-no , so try to avoid loading images in a large loop
3- Endless loops
Endless loops are just bad, for example looping inside a map and inside it you are looping inside a list and within you are also looping in a list items
just avoid multiple loops within 1 loop.
Other than the above i think you are good to go, the memory management is always handled by the OS but sometimes there are "developer mistakes" which can lead to postpone the garbage collection and that would cause a memory exception/leak