If you want to have multiple files for the same field you would have to write your own field and widget based on the form field you have found otherwise have a separate model for file with a foreign key to your main model and use ModelInline.
models.py
class Page(models.Model):
title = models.CharField(max_length=255)
class PageFile(models.Model):
file = models.ImageField(upload_to=settings.FILE_PATH)
page = models.ForeignKey('Page')
admin.py
class PageFileInline(admin.TabularInline):
model = PageFile
class PageAdmin(admin.ModelAdmin):
inlines = [PageFileInline,]