Image picker uploaded image name can not get

I've use image picker & also upload an image in folder successfully but uploaded image name cannot get in twig file.

I've tried below

{% if sliderfield.custom_file %}
<img src="{{ url('theme://img/') }}{{ img.custom_file }}" alt="{{ img.text }}"
{% endif %}

ymal file

sliderfield:
type: tab
title: slider
fields:
header.slider:
type: list
label: slider
fields:
.slidertitle:
type: text
label: Slider Title
id: text
.sliderdesc:
type: textarea
label: Slider Description
id: desc
.custom_file:
type: file
label: A Label
destination: 'theme@:/img'
multiple: true
limit: 5
filesize: 1
accept:

• image/*
  .text:
  type: text
  label: Alter Text