[SDPhantom]

Here's my take on it. I would suggest trying to insert custom pins in the MapCanvas system, but I haven't dug around it ever since it was implemented. There isn't a way to delete UI objects without a logout or UI reload, so you have to create a pool of them by storing them in a table you grab from. There's no reason to loop through and hide the icons OnHide. The "cleanup" is handled with the next OnShow.

local IconTextures={};--    Table to store our textures
 
local function MapTest_UpdateIcons()
    local numshow=(amount_to_be_decided);
 
    local textureindex=1;-- We increment this when we grab a texture
    for index=1,numshow do
        if (logic_to_be_decided) then
            local icon=IconTextures[textureindex];--    Fetch texture from table
            if not icon then--  Texture not created yet (We don't want gaps in the table or it'll mess with the table length operation we use later)
                icon=WorldMapDetailFrame:CreateTexture(nil,"OVERLAY");
                icon:SetTexture("Interface\\AddOns\\MapTest\\AvailableQuestIcon.blp");
                icon:SetSize(16,16);
 
                IconTextures[textureindex]=icon;--  Store in table
            end
 
            local width,height=WorldMapDetailFrame:GetSize();
            icon:SetPoint("CENTER",WorldMapDetailFrame,"TOPLEFT",(XPos/100)*width,(YPos/100)*height);-- Move to coordinates
            icon:Show();--  Show texture
 
            textureindex=textureindex+1;--  Increment index
        end
    end
 
    for index=textureindex,#IconTextures do--   Iterate through icons we haven't updated yet (textureindex will point to the first unused in the list, doesn't run if there are no unused textures (start > end))
        IconTextures[index]:Hide();--   Hide them
    end
end
 
WorldMapFrame:HookScript("OnShow",MapTest_UpdateIcons);--   Map Opened
WorldMapFrame:HookScript("OnSizeChanged",MapTest_UpdateIcons);--    Map Resized