I have been trying to create a theme based on the luma theme.
I have successfully created the new theme, but once I switch over to the new theme, the sample data does not show up any more.
How to get Sample Data and Logo in custom theme.
By Default magento 2 with sample data comes with luma themes.
In Luma Themes all static block and Top category page called from Widget.
You can check widget from
Content -> Elements -> Widget
There are list of widget are available here and all widget are assinged to Magento Luma Themes.
So when we create new theme, Based on parent luma theme, All sample data are missing in our new theme because widget are not set in Our custom theme.
If you want to display content same as Luma theme, You have to create new widget same as Luma theme from widget section from admin.
For Set Your Custom Theme logo,
You have to set from backend,
Content -> Design -> Configuration menu
Click on your current theme Edit link,
Go To Header section,
Click on Upload button on Logo Image, Click Save Configuration.
Clear Browser cache and system cache.
Your Logo are Set for your custom theme.
If you know about databases and SQL and you know what you are doing and don't have the time to create all the widgets again in your custom theme, you can change the field theme_id in the tables
layout_link to your new theme_id. After clean caches and static content, the homepage, category blocks, etc of Luma will appear in your theme.
A database backup is always recommend before directly changing database data.