Several filters capable of turning over 10-15 times your tank volume an hour
So 900-1350 gph.
I would seriously look at the FX5, it an awesome filter. I have a Rena XP4 and FX5 on my 75g tank...water is spotless.
Decorations you would be looking at are lot of ROCKS, sand as the preferred substrate as that is what Lake Malawi is.
I would look at 2 x 200w heaters possibly inline like these
Find out here
about cycling...there is no set time and each tank is different but 6-8 weeks would be about right for a 90g tank.
It is essential that you get a test kit...look at the API freshwater Master Kit.
Regarding the 3d background, I cannot help you with that as I do not have one.
Do you have any stock list as yet other than "Africian Cichlids"? types etc?