Can anyone help me to do this? I have literally no experience in using Xml or Gui, I read through the threads on faction portraits, downloaded the example major faction mod and got as far as changing the mod name, description, picture with success. But now I am stuck as to how I change leader portraits, faction names in the drop down menu, the large background image etc. 

Any help at all for a complete beginner would be much appreciated.

Also, I have created Custom Factions in-game, is there any way to change the images for these?

For anyone coming here looking for help too, I looked around on youtube and this video helped alot with getting started

https://youtu.be/k6ge4vLHUng 

Artemis-6 wrote:

Also, I have created Custom Factions in-game, is there any way to change the images for these?

Here is a way to change the images of your Custom Faction created in-game with other images from the game, for example heroes , change the images of your custom population and change the introduction text of your custom faction, when starting the game:

1. Create your Custom Faction in-game. Close the game

2. Change the following two files in your documents folder

Custom Population/YourPop.xml

In PopulationDefinition change AffinityName="..." in somethin easer to remeber, for example AffinityName="AffinityCustomPop01"
Change AffinityMapping Name="..." to AffinityMapping Name="AffinityMappingCustomPop01"

YourFaction.xml

Change MajorPopulation Affinity="..." in MajorPopulation Affinity="AffinityCustomPop01"

3. Change the following files in your ES2 installation folder (make BackUp)

FactionTraits[AffinityMapping].xml

Copy and paste a complete <FactionAffinityMapping>...</FactionAffinityMapping> block from another major faction. In this new block change FactionAffinityMapping Name="..." to FactionAffinityMapping Name="AffinityMappingCustomPop01".
If you want, change the Hero Arguments="..." to a Hero ID of your choise. This will change your starting hero.

GuiElements[Affinities].xml

Copy and paste  a complete <AffinityGuiElement>...</AffinityGuiElement> Block from another major faction.

Change the name in "AffinityMappingCustomPop01"

Change the description in %AffinityCustomPop01Description

Change the icons accordingly (important are Small, Medium, MediumIverted, Large, Mood). For example:

    <Icons>

      <Icon Size="Small" Path="Bitmaps/Atlased/Affinities/AffinityPilgrimsSmall" />

      <Icon Size="Medium" Path="Bitmaps/Atlased/Affinities/AffinityPilgrimsMedium" />

      <Icon Size="MediumInverted" Path="Bitmaps/Dynamic/Affinities/MediumInverted/AffinityPilgrimsMediumInverted" />

      <Icon Size="Large" Path="Bitmaps/Dynamic/Affinities/AffinityPilgrimsLarge" />

      <Icon Size="Leader" Path="Bitmaps/Dynamic/Affinities/AffinitySaphronsLeader" />

      <Icon Size="Mood" Path="Bitmaps/Dynamic/Affinities/AffinityPilgrimsMood" />

      <Icon Size="SmallExtended" Path="Bitmaps/Atlased/Notifications/NotificationEmpireMet/NotificationMajorEmpireMetSophonsSmall" />

      <Icon Size="MediumExtended" Path="Bitmaps/Dynamic/Notifications/NotificationEmpireMet/NotificationMajorEmpireMetSophonsMedium" />

      <Icon Size="Loading" Path="Bitmaps/Dynamic/Moods/LoadingScreen01" />

    </Icons>

Search the file for other faction, for example the pilgrims, to see how there paths are defined. The example above will give your custom population the look of the pilgrims.

Change ModelPath accordingly, for example:

<ModelPath>Prefabs/Gui/AnimatedPortrait/AnimatedPortraitPilgrim</ModelPath>

The above example will give your leader the appearance of the pilgrim hero. Search the file GuiElements[Heroes].xml to find the hero ModelPath you want to use as a leader.

ES2_Localization_assets_Locals.xml (for your language)

Add the following lines:

              <LocalizationPair Name="%AffinityGameplayCustomPop01IntroductionTitle">I am an introduction</LocalizationPair> 

              <LocalizationPair Name="%AffinityGameplayCustomPop01IntroductionDescription">I am a description</LocalizationPair>

              <LocalizationPair Name="%AffinityCustomPop01Description">I am a custom population</LocalizationPair>

The first will change the title of the introduction screen, which pops up in a new game. The second changes the description in this pop up. The third changes the tooltip lore description of of your custom population.

I hope it is understandable. Sorry, i am not a native speaker.