"Moab is my wash basin. I will throw my sandal on Edom" (60:8). What do these pictures mean?

The psalm doesn't explain them, and these notes won't go beyond the lexicons. In Hebrew wash basin is two words: sir, which Brown-Driver-Briggs gives as "pot", and rachats, which it gives as "washing" (tap wash basin). Sandal is na'al, which Brown-Driver-Briggs gives as "sandal, shoe"; Strong's adds, "sometimes as a symbol of occupancy, a refusal to marry, or of something valueless", and doesn't say which of these, if any, fits this verse (tap sandal). Psalm 108 has the same Hebrew for both lines, and the WEB words them "Moab is my wash pot. I will toss my sandal on Edom" (Psalm 108:9). What the verse does make plain is who says it: these are God's words, spoken "from his sanctuary" (60:6), and they come right after "Gilead is mine, and Manasseh is mine" (60:7). These notes don't apply Moab, Edom or Philistia to any people today.