Some random cards I thought up while procrastinating...
Innkeeper
[Action]
Cost: $5
+1 Action
You may reveal and discard an action card from your hand. If you do, +2 cards and gain a silver into your hand. Otherwise, trash a card from you hand.
This doesn't need the "reveal and". The trash clause seems unrelated to the rest.
"Reveal and..." is fixed, I have the trash clause so this isn't completely useless when you only have it in your hand, but I would take other suggestions as to what that effect should be.
Lucky Coin
[Treasure]
Cost: $2
Worth $1
When you gain this, choose a card you have in play. Either trash it or put it on top of your deck.
When you trash this, +$3.
The problem with "when you trash" +$ is that it doesn't trigger (or at least triggers as a detriment) when trashed with Rogue, Knights, Sabotuer, or Swindler. This is also much better than Loan.
Okay, I got rid of the "+$3" in favor of "gain a silver into your hand". Why do you think it is better than Loan? The effect only triggers once, when you buy it, and it won't even search your deck for a treasure to trash.
Artist
[Action]
Cost:$6*
+3 Cards
+$2
Trash a card from your hand. Discard a card. Put a card from your hand back on top of your deck. Put an art token on your artist mat.
This card costs one less for each art token on your artist mat. When you gain this, remove 6 art tokens from your artist mat.
I would need to see artist at work. In a hand with 7 cards in it, there is nearly always one card you can't play (especially with no remaining actions), one thing to trash, and one victory/curse to discard without problem. Compare to Courtyard +$2. This card is likely worth $6 at all points, so not worth its gimmick. The gimmick might work elsewhere, though.
The problem with the gimmick is that it cannot be on a card that you REALLY REALLY REALLY want to have extra copies of, otherwise it makes buying that card into an easy decision. The card also cannot have self-synergy, because having a copy of it already makes it easier to buy more.
Artist is a card that you probably don't want a ton of copies of, unless you've carefully built your engine around it. It is very powerful early game, but as you start to green it becomes very weak...forcing you to trash a card, not increasing your hand size, and not really giving you a lot of money or +buys. With that said, I could see moving the amount of cards drawn down to +2 cards. Do you think that's more balanced?