Hi Benji
Are you importing the same or a new image and rename it to have same name? If you are continually importing the same image or a new image with the same name, you will get "bg_1.jpg", "bg_2.jpg", "bg_3.jpg", etc and that is by design. Also, you can rename the asset in the library by double click on the asset or right click on it to use "Rename" option in the context menu. No need to go to the assets folder to rename the asset. For deleting unused items, you can use the "Trash bin" icon or right click on the item and choose "Delete" from the context menu.
Please visit our help page for Library:
Thanks,
Jason (GWD team)