Of course you can. You can directly create a thread in Marketplace>Goods (
https://bitcointalk.org/index.php?board=51.0) to list your paintings or do a collaboration to trusted member here to launch the sales for a cause to your paintings to attract more buyers that will buy it for a good amount of money. I highly suggest to contact minerjones, krogoth, Hhampuz, and other trusted member in collectible section to help you with the sales. Looking forward to your painting sales and I really want to help.
I'm also in favor of this advice. I guess
minerjones is the man. Minerjones is the most most trusted person on the forum. He/she is both a re-shipper and an escrow. But my reservation is that OP will have to send the paintings to minerjones first before things could be set up. So, that will require OP to spend first before getting the funds that's needed for grandma's operation.
OP you can buy a copper membership so that you can post an image even if you are a newbie.
Forget about this as OP is trying to raise funds for his/her grandma's bone marrow transplant. He/she is definitely short of cash so I think he/she should be avoiding unnecessary expenses. I'm sure somebody who's got the rank would readily quote the image for him/her for everybody to easily view it.
Edit: OP has responded to this already.
Thank you for the advise and help Sir! i don't have 20$ to pay for the Copper member, as i will use it to buy food for my siblings instead. I will try to put my activity to 30 so i will able to post my images. Thank you so much!
Forget about the 30 activities.
Since you are in a really bad situation right now, just post the sale in the
goods section, the price you're willing to sell it for, the place where you're shipping from, that you are willing to use an escrow for the transaction, and link of the image along with your username here and the present date.
Don't worry about the image not showing, I'm sure somebody would be willing to quote it for you so that everybody could see it. If none, just PM and I'll quote it for you.