Change logo, skin and style in OBIEE 12c

 Change logo, skin and style in OBIEE 12c 

For changing style and skin you should use default OBIEE doc
Customizing the Oracle BI Web User Interface

Quick workaround if you want only change logo 

You logo should be near 136x28

Update logo in folders
/oracle/product/fmw1221/user_projects/domains/bi/servers/bi_server1/tmp/_WL_user/analytics/za01ic/war/res/s_Alta/master/

/oracle/product/fmw1221/user_projects/domains/bi/servers/bi_server1/tmp/_WL_user/analytics/eiguw6/war/res/s_Alta/master

/oracle/product/fmw1221/user_projects/domains/bi/servers/bi_server1/tmp/_WL_user/bimad_11.1.1/hkbdzw/war/theme/alta/master/

 /oracle/product/fmw1221/user_projects/domains/bi/servers/bi_server1/tmp/_WL_user/bipublisher_11.1.1/to5gma/war/theme/alta/master/

/oracle/product/fmw1221/user_projects/domains/bi/servers/obips1/tmp/earmanager/analytics/iNcTF3GuQnj4Ii0d5ex_mg/res/s_Alta/master/

Restart OBIEE and clear browser cache.