api: Add low level control methods for the login screen background

runelite-mixins/src/main/java/net/runelite/mixins/LoginScreenMixin.java

@@ -76,6 +76,26 @@ public abstract class LoginScreenMixin implements RSClient
 		}
 	}
 
+	@Inject
+	public void setLoginScreenBackground(SpritePixels background)
+	{
+		assert client.isClientThread() : "setLoginScreen must be called on client thread";
+		loginScreenBackground = background;
+		client.clearLoginScreen(false);
+	}
+
+	@Inject
+	public void setLoginScreenLeftTitleSprite()
+	{
+		setLeftTitleSprite(0);
+	}
+
+	@Inject
+	public void setLoginScreenRightTitleSprite()
+	{
+		setRightTitleSprite(0);
+	}
+
 	@Inject
 	@FieldHook("leftTitleSprite")
 	static void setLeftTitleSprite(int idx)