Upload multiple files to your theme assets
Theme assets should not be confused with product images or uploaded files. To bulk-upload product images, you must import a product csv. For other files, you must upload them one-by-one on the Files page of your admin.
Here's how you can upload many images or files to your theme assets without having to upload them one by one:
Export a copy of your theme.
Unzip the archived theme on your desktop (or wherever you downloaded the .zip file).
Select all your images or files that you want to add to your theme assets, and copy or move those to the
assetssub-folder of your extracted theme folder.
Compress your modified theme folder as a .zip archive.
In your Shopify admin, import the modified theme
Your modified theme will appear on the Themes page of your admin.
Uploaded themes must be smaller than 20 MB. If you are having trouble importing your theme, check to make sure it is smaller than 20 MB.