Custom asset icons

  Style = MakeShareable(new FSlateStyleSet("StyleName"));
 
    FString StyleDirectory = IPluginManager::Get().FindPlugin("PluginName")->GetBaseDir() + "/Resources/";
    Style->SetContentRoot(StyleDirectory);
 
    Style->Set("ClassThumbnail.NameOfYourAssetClass", new FSlateImageBrush(Style->RootToContentDir("Your_Icon.png"), FVector2D(128.0f, 128.0f)));
    FSlateStyleRegistry::RegisterSlateStyle(*Style );