Default office excel report will be populated with oracle logos and footage, if you want to have customization as per your company, then here is a solution.
All these information is stored in template files, which are located at C:\Program Files\Oracle\BIOfficeExcel\Template\ on disk with file names as OBIReport.xlt, OBIReport.xls modify these files by remove oracle logos, add your logos, header, footer, back ground logo etc and save. Upon logon to office add-ins you will be able to see reports with your template.
Helpful articles,
1) Step by step on Using Office Add-ins with OBIEE in Oracle tech web
