In myapp/admin.py:

from django.contrib import admin

class MyModelAdmin(admin.ModelAdmin):
    # ...
    def changelist_view(self, request, extra_context={}): 
        other_objects = OtherModel.objects.all()    
        extra_context['other_objects'] = other_objects
        return super(MyModelAdmin, self).changelist_view(request, extra_context)

In the file templates/admin/myapp/change_list.html，wherever you need it, you can access to your other_objects like this:

{% for obj in other_objects %}<h1>{{ obj.id }}</h1>{% endfor %}