Google has announced changes to the protected sheets and ranges functionality in Sheets, which is intended to provide a deeper level of control when locking sections of content in a spreadsheet. The improvements include:
Google has also made it easier to improve your invoices, reports, or other spreadsheets with images or logos, in the frozen sections. To insert an image in a frozen section of a Sheet, select a cell in the row and click Insert > Image. The image can then be resized and moved as appropriate. Note that this feature only works in the new Google Sheets.
For more information, see Protected sheets and ranges improvements in Google Sheets and Images in frozen sections in Google Sheets.