Yes it’s possible to use the main images only for the slider. For this you need to upload background images only.

Try to upload the images as per dimension details given near the image upload field.

If you wish to have more than 3 sliders , you need to alter the liquid code as follows. Just duplicate the slider style that you want and place it next to third slider. Change the number (1/2/3 to 4/5 etc..)

As well as change the option values too.

Finally save and configure related values at customization panel.

E,g

{% if section.settings.slide_1_bg_image != blank %}

<img src=”{{ section.settings.slide_1_bg_image | img_url: “master” }}”  alt=”{{ section.settings.slide_1_title }}” title=”{{ section.settings.slide_1_title }}” ”  width=”1750″ height=”800″ data-bgposition=”center center” data-bgfit=”cover” data-bgrepeat=”no-repeat” class=”rev-slidebg” data-no-retina>

{% endif %}

This can be changes into

{% if section.settings.slide_4_bg_image != blank %}

<img src=”{{ section.settings.slide_4_bg_image | img_url: “master” }}”  alt=”{{ section.settings.slide_4_title }}” title=”{{ section.settings.slide_4_title }}” ”  width=”1750″ height=”800″ data-bgposition=”center center” data-bgfit=”cover” data-bgrepeat=”no-repeat” class=”rev-slidebg” data-no-retina>

{% endif %}