Can I put decals directly over Testors' Metalizer Sealer?

Testors metalizer sealer is a clear gloss.

You should have put the decals on before the sealer.  However, I think you can apply decals over the thoroughly cured sealer, then spray another coat of metalizer sealer.  This stuff works like decal solvent on the decals, so don't be worried if they wrinkle up.   Just don't touch them and leave them sit overnight.  You should be fine with this.

Yes you can put decals on the cured and buffed metalizer. I did a 1/48 B-29 about a year ago and did not spray a sealer or clear coat over it. (seem to dull the finish slightly). The decals were put on with microscale set and then used microscale sol. Decals still look great.

Holy Cow!! That is really an impressive portfolio of model airplane models in your Flickr account. Very nice!