It is possible to slightly change the User-Agent string
Right now the string is something like: "/Satoshi:0.9.1/" or "/Satoshi:0.8.5/"
List of nodes is here https://getaddr.bitnodes.io/nodes/1407404879/?q=United%20States

Just change your bitcoind and set this string to "/Satoshi:0.9.1-Donate-1MyBitcoinAddressForDonations/"
(this can be even configurable option in .conf file)
Everyone will see that the node is really exists and connected

In fact, I do not think that fullnode owners should ask donations. The rest of network is obliged nothing to them.