Will I lose anything if I change versions (excluding custom coding)?

So, I'm here to ask if I will lose anything major if I change from phpBB2 to phpBB3. By "major," I mean members, background, logo/banner, general appearance design, etc. I know that there is an option to keep your current style when you switch versions, but I am just wondering if there is anything at all that will be lost. Will I lose any of my stored pictures that I've used for things like topic/forum buttons/icons? Do the losses only apply to changes that you've made in the template or CSS? Just how extensive are the losses?

I wasn't sure whether to post this in the Design & Appearance section or the Administration Panel section. I would also like to say that I've used the search function quite a few times and haven't found many topics with a similar problem to mine. There was one, but the detail given was very miniscule. I also checked the Frequently Asked Questions topic but couldn't find anything too informative on this. I'm sorry if this has been asked before.

Any help is appreciated.

Hi,
You will keep it when you change your forum version, Except the following i stated below:

~ PHPBB 2 Template (Default & Custom)
~ Themes (I Don know will it lost if version been change)
~ CSS
~ Banner, Navigation & Background Picture.
~ Icon like Topic, Category.

Hope i can help you .