[Garkin]

As Merlight said, you will need to convert image to DDS first: http://www.esoui.com/forums/showthread.php?t=127

If you want to display image, you will need to create control which can display it - the easiest is using texture control.

Simple example in XML:

<GuiXml>
    <Controls>
        <TopLevelControl name="WindowName" hidden="true">
            <Dimensions x="256" y="256">
            <Anchor point="CENTER">
            <Controls>
                <Texture name="$(parent)Image">
                    <AnchorFill />
                </Texture>
            </Controls>
        </TopLevelControl>
    </Controls>
</GuiXml>

The same as above in Lua:

local tlw = WINDOW_MANAGER:CreateTopLevelWindow("WindowName")
tlw:SetDimensions(256,256)
tlw:SetAnchor(CENTER)
tlw:SetHidden(true)
 
local image = WINDOW_MANAGER:CreateControl("WindowNameImage", tlw, CT_TEXTURE)
image:SetAnchorFill(tlw)

Now just check if you image path exists and if so display it:

local function QuestMaps()
    local zoneIndex = GetCurrentMapZoneIndex()
    local imgQuests = questImage[zoneIndex]
    if imgQuests ~= nil then
        WindowNameImage:SetTexture(imgQuests)
        WindowName:SetHidden(false)
    else
        WindowName:SetHidden(true)
    end
end

(untested, but I think you have an idea what I mean)