Tell Me about Postcards

[rustyattic]

Do you have any tips when searching for valuable/popular postcards?  (I'm considering single cards that easily fetch $10 popular)  I've accumulated a few shoe boxes full and need to start selling them.  ~60% have writing on them/gone through the mail.  Does that devalue them a lot? 
Here's some pics of one's I like so far

[Ipcress]

Not sure about in the US but here in the UK

Real Photo postcards from before WWII - cards which depict streets, shop fronts etc which are no longer there. Sometimes sell for hundreds per card.
Military cards - especially the embroidered silks or others sent from the front.
Louis Wain etc. Sometimes known as " artist signed ".
Actresses, " beauties " as they're known.
Then those glamorous ones by certain artists like Kirchner

There's also another side to the card which includes scarce cancellation marks, significant postal dates or marks for certain post offices

And cards from South East Asia are increasing in value

[Rauville]

From the cards you've pictured, I would pick the "Santa / Child / Reindeer(?)" as the most desirable.

(I see you have a Corn Palace card. Interesting place with an interesting background.)
https://cornpalace.com/Festival/festival-history.php

[greenacres]

Ruby Lane has a great selection of antique postcards with prerty acurate prices.  Everyone has their thing. Art deco cards can be very collectible. I like the RPPCs. I try collecting pit bull post cards but people are getting out of control.  Some were $35. or $40. dollars, but now I see some crazy things. I've seen some on ebay that are ridiculous.  So it really depends on the topic and rarity.

[rustyattic]

gold rush maybe?

[greenacres]

Really nice postcards!