I'm working on Linux release for some time and I feel I need to have a fun little bit. I've googled for a look & feels which would work on linux and found a page http://www.javootoo.com/ with custom L&Fs and tried to plug some of them into wtk toolbar. Some are free, some commercial, some work only on windows ...

Start with jdk linux native look and feel. jdk 6 native L&F shows improvements comparing to jdk 5. But notice separators in the JToolBar, they aren't vertical.

jdk 5

jdk 6

Alternative look and feels
To plug-in L&F just edit ktoolbar script. Put L&F jar on classpath and set property -Dkvem.lookandfeel. An example for synthetica L&F:

-Dkvem.lookandfeel="de.javasoft.plaf.synthetica.SyntheticaStandardLookAndFeel"

Napkin

Synthetica Green and Dream

Tonic slim

Tiny YQForest

L2FProd skins
You can try L2FProd skins if you edit ktoolbar starting script to look like this:

java -Dkvem.home="${KVEM_HOME} \
    -Djava.library.path="${KVEM_HOME}/bin \
-cp $KVEM_LIB}/lf/skinlf.jar:${KVEM_LIB}/kenv.zip:${KVEM_LIB}/ktools.zip:${KVEM_BIN}/JadTool.jar:${KVEM_BIN}/MEKeyTool.jar:${KVEM_LIB}/customjmf.jar:${KVEM_API}/j2me-ws.jar:${KVEM_BIN}/schema2beansdev.jar:${KVEM_BIN}/j2me_sg_ri.jar:${KVEM_BIN}/jaxrpc-impl.jar:${KVEM_BIN}/jaxrpc-api.jar:${KVEM_BIN}/jaxrpc-spi.jar:${KVEM_BIN}/activation.jar:${KVEM_BIN}/mail.jar:${KVEM_BIN}/saaj-api.jar:${KVEM_BIN}/saaj-impl.jar:${KVEM_BIN}/xsdlib.jar \
Skinit -pack ${KVEM_LIB}/lf/themepack.zip com.sun.kvem.toolbar.Main "$@"

Evenif this is a linux script I believe you can edit also win32 ktoolbar.bat script acordingly. You just need skinlf.jar on the classpath and download apropriate themepack.zip. Here are some of them:

L2FProd cell shaded

L2FProd Graphite

L2FProd OpusOSDeep

L2FProd AAToxic