Here we are posing a small 11 kb image.
This image must be serialized using base64 encoding and passed into the field encodedRawCreative.
To encode an image you can use https://www.base64-image.de/ or find a library for the language you are using to do it programmatically. There is an example in the python code that accompanies this tutorial
For this call you will see that you need to pass in the Advertiser ID when posting the Creative.
curl -X POST -H ‘auth:eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzZWF0SWQiOjEwMDAsInVzZXJJZCI6NCwiZXhwaXJlcyI6IjIwMjAtMDgtMjUgMDI6Mjc6MTYifQ.JpVp62T-VEbuxquTXHXaKqhrqEIef1Hq3PpaRgExzrg’ -d ‘{
“name”:”testSmallCreative”,
         “pontiacAdvertiserId”:1713,
         “creativeProperties”:{
            “clickURL”:”http://pontiac.media”,
“encodedRawCreative”:”/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDADIiJSwlHzIsKSw4NTI7S31RS0VFS5ltc1p9tZ++u7Kfr6zI4f/zyNT/16yv+v/9////////wfD/////////////2wBDATU4OEtCS5NRUZP/zq/O////////////////////////////////////////////////////////////////////wAARCAD6ASwDAREAAhEBAxEB/8QAGQABAQEBAQEAAAAAAAAAAAAAAAECAwQF/8QANxABAAIBAwMDAwMDAwMDBQAAAQI…
…JitQd8lVHIJtT57YEcKOBHAmAfvgPvgMCGFXAGRY0YIpkqxoxVjRkajZirGjJWo2ZKrcciV0MsRowjWCmEocnzlSqcn/APTlSsvB8OWJWX/bLGaw85qM1l4yxmsOEqPGEZcDDgjLzgR74WI4rUHIsRyERwI4UwRHAhyYB5cUMBgf/9k=”,
“width”:300,
“height”:250
},
“status”:1,
“creativeType”:”image”
}’ ‘https://api.pontiac.media/pontiac/creative?advertiser-id=1713’
(see full encoded Creative here: Encoded Creative)
 
Response with the wrapper and read only fields:
{“timestamp”:”Mon Aug 24 19:03:28 UTC 2020″,”response”:{“Creatives”:[{“pontiacCreativeId”:28214,”seatId”:1000,”name”:”testSmallCreative”,”pontiacAdvertiserId”:1713,”creativeProperties”:{“clickURL”:”http://pontiac.media”,”thirdPartyPixelsIds”:[],”encodedRawCreative”:”/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDADIiJSwlHzIsKSw4NTI7S31RS0VFS5ltc1p9tZ++u7Kfr6zI4f/zyNT/16yv+v/9////////wfD/////////////2wBDATU4OEtCS5NRUZP/zq/O////////////////////////////////////////////////////////////////////wAARCAD6ASwD…
…wI4UwRHAhyYB5cUMBgf/9k=”,”width”:300,”height”:250,”segmentPixelIds”:[]},”status”:1,”auditData”:{“status”:”pending”},”creativeType”:”image”,”clickTracking”:0,”soonToExpire”:0,”isSensitive”:0,”categories”:[],”isMalicious”:0,”isUnusable”:0}]},”accountStatus”:1,”seatId”:1000}

(see full Response here: Response)
 
From this we will need the pontiacCreativeId. We will pass this in when making the Line, in this example it is 28214.