fix: update default values for docker image, add image for v15 #1267

Job	Run time
pr-test (one-chain-custom-scripts.yaml)	3m 36s
pr-test (one-chain.yaml)	3m 44s
pr-test (one-custom-chain.yaml)	3m 39s
pr-test (multi-validator.yaml)	3m 59s
pr-test (simapp.yaml)	3m 17s
pr-test (one-chain-starship-faucet.yaml)	3m 3s
pr-test (multi-validator-starship-faucet.yaml)	3m 38s
pr-test (one-chain-cometmock.yaml)	2m 51s
pr-test (one-cosmoshub-starship-faucet.yaml)	3m 8s
pr-test (eth-lite.yaml)	2m 17s
	33m 12s

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