Try to put the fontstring and texture on the same frame, and change the texture's drawlayer to artwork.
Lua Code:
local iconFrame = CreateFrame("Frame", nil, frame)
iconFrame:SetSize(32, 32)
iconFrame:SetPoint("TOPLEFT", x, y)
local itemTexture = iconFrame:CreateTexture(nil, "ARTWORK")
itemTexture:SetAllPoints()
local itemCountText = iconFrame:CreateFontString(nil, "OVERLAY")
itemCountText:SetPoint("BOTTOMRIGHT", -4, 4)
itemCountText:SetFont("Fonts\\FRIZQT__.TTF", 11, "THICKOUTLINE")
itemCountText:SetJustifyH("RIGHT")