Open the es_settings.cfg file (you can find it in \\retropie\configs\all\emulationstation) and set the theme to the default one, by changing the ThemeSet option to carbon:

<string name="ThemeSet" value="carbon" />

@mitu I see what I did. I got it to work. Thanks for the help. Would you have any idea why my video snaps for game previews are working in Attract mode but not emulation station? I would love to use this BTTF theme all the time but trying to find a game to play without preview is challenging.
Again, thanks for your help

I just want to use a theme that is already set up for three media types. That will look much better than forcing a third image into one that's designed for two. I just thought there would be more than the two I mentioned...

@Super-Retropie Cool! Thanks for your hard work!

Thanks.

If there's anything you can just point me to that I can try to look at for a fix, I'd appreciate it.

OK, I found what was causing this issue : I've put the metroid folder in /home/pi/ in order to copy it in /etc/emulationstation/themes/showcase/ and it was interfering...

You can look at the list of the themes available in RetroPie here. The list format is 'Github user', 'Github theme repository', so

RetroPie carbon-centered

can be found at https://github.com/RetroPie/es-theme-carbon-centered. Once you have the theme's repository, you can download the theme as a 'zip' file using the Code button

Most of the themes are not designed for a portrait mode - but you can try some of the 4:3 and CRT designed themes. I remember one them ( crt-centered ) had a simpler layout, with video on top of the gamelist, which would maybe fit the bill.

EDIT: you can run the theme-gallery from the Configuration/Tools->Emulationstation to get previews for different themes, just to see how they fit on your screen.

Alright thanks! Last question (I would like to work on a new theme) Is a PS4 like UI possible with Retropie? So the selected icon isnt always in the middle? Thanks!

Theme is coming along nicely now. I intend to do a series (I got another 4 weeks minimum of furlough) of themes, based on hit SyFy channel TV programmes, starting with Warehouse 13.
I am doing 1 system at a time and testing it, having different characters and artifacts for the system screen, and basic screen, with a warehouse type tag for each.
So each one will look a bit like this;

SYSTEM Screen

BASIC Screen

However, I am having issues with the Detailed/Video Screen. I have this so far;

But what I want, is just to incorporate a screen shot of the scraped game, then a video snap of the game, but I want it so that it is in the "screen" of the following image. I am happy where the gameslist is, as I wanted it in the lid of the farnsworth (fans will know what I mean)also with the positioning of the other Meta data and the console. This is the image.

Is there anyway of manipulating the scraped image so they appear in the round window. I have tried most things, but don't know how to display only screenshots and videos, and discount the marquees and the boxart. With the one I have I was able to make it fit by making the screen square.

As always, any help very much appreciated.

If you want to take a screenshot of just your current active window, type Alt-PrtSc instead of just the PrtSc key.

Get a SDcard testing tool (like H2testw or F3X) and check if your card is ok. If not, then you'll need a different SD card, otherwise try again to re-image.
You can also have issues from the power supply - the 3B model needs a 5V, 2.5A power supply - if you're using a simple charger I strongly advise to get a proper one.

I am new to this game as well, but before anyone asks, I know one person who is sick and tired of saying it, you need to fill in/read this first, that way you will get more help.
https://retropie.org.uk/forum/topic/3/read-this-first

As for your questions, even though I am still a novice I may be able to help on A

If you hit the Start key and bring up the main menu, you can go down to UI settings, and change the themes etc. On the Gamelist View Style, there is an Automatic option, every timeI have used this it will display both boxart and video's. It also does the same with video's settings.
If your getting black when it fades from the boxart image, it may not necessarily mean the video isn't there. It may have scraped but the video doesn't have the right codec for the Pi. I myself had this issue.
If you follow this guide https://github.com/hiulit/RetroPie-Convert-Videos it may help with any non-playing videos. It certainly did mine.
Also if you look in the Media or images folder that is associated with the system you are playing on you can see what images are there, and what videos.
Put on your PC a program called WinSCP and you can look at your pi directory from the PC and do all the necessary from that.

B0 I am sure somebody will correct me, but also if you use WinSCP you can look in the Media/image folder for MAME and you might find the image used for emulationstation. But you will probably have to edit the .cfg file associated with this, in order to display the image you want.

Hope it has been some help.

@LiveFastCyYoung Sure, go ahead. Just credit me

@Thorr69 Hi, thanks for the suggestion - but would that not also hide it for all my 'systems', not just the Retropie menu?

@Mental I’ll be adding more colors soon 👍🏻